Anna Potocki
email: anna.potocki@univ-grenoble-alpes.fr.

Julie Ayroles

Jean-François Rouet

A short teacher-led intervention using direct instruction enhances 5th graders' purposeful reading skills

Keywords: purposeful reading, primary school, instructional resources, training program

Proficient readers use strategies in order to achieve various types of reading purposes. However, purpose-driven strategies are seldom taught in elementary schools. Based on current theories of purposeful reading and direct explicit instruction, the present study developed and tested an instructional program to promote fifth graders' purposeful reading skills. Teachers from five different schools, representing 10 classes, were trained to implement the program. The intervention included two weekly 45-minute workshops over a period of five weeks. Using a quasi-experimental design, participating classes were assigned to an experimental group (n = 78) or an active control group (n = 89). Trained students outperformed controls on post-tests assessing each purposeful reading component. However, effects on an integrated and unguided purposeful reading tasks did not reach significance. The study suggests that the explicit teaching of purposeful reading strategies can effectively support students' skill acquisition. The conditions needed for innovative interventions to yield robust and lasting outcomes are discussed.

A short teacher-led intervention using direct instruction enhances 5th graders' purposeful reading skills

Introduction

Reading takes place in a diversity of contexts (Snow et al., 2002) and for a variety of purposes (Britt et al., 2018). Although any form of reading arguably comes with a purpose, the phrase "purposeful reading" emphasizes the need for the reader to actively set goals based on external or self-generated instructions, and to implement goal-relevant strategies [START_REF] Mccrudden | Relevance and goal-focusing in text processing[END_REF][START_REF] Vidal-Abarca | Individual differences for self-regulating taskoriented reading activities[END_REF]. For instance, depending on their goals, mature readers may generate different types of inferences while reading (e.g., van den Broek et al., 1995); or they may decide to skim some portions of a text and to focus on task-relevant segments (e.g., [START_REF] Kaakinen | Task relevance induces momentary changes in the functional visual field during reading[END_REF]. Critical to the construct of purposeful reading is the view that reading strategies and outcomes depend on readers' understanding of the task to be achieved (i.e., their task model, [START_REF] Rouet | Relevance processes in multiple document comprehension[END_REF], and on their ability to make goal-relevant reading decisions (see RESOLV model, Britt et al., 2018).

The need for effective literacy skills extends to online information environments.

Although Web search engines and other online reading tools provide increasingly efficient tools to support user search, their benefits are pending on readers' acquisition of online reading skills [START_REF] Leu | New literacies: A duallevel theory of the changing nature of literacy, instruction, and assessment[END_REF]Salmerón et al., 2018). In addition, key strategic processes such as skimming a page to locate a piece of information are no less demanding when reading online compared to printed text [START_REF] Potocki | Children's visual scanning of textual documents: Effects of document organization, search goals and metatextual knowledge[END_REF]. In fact, online reading may entail as many, if not more challenges to the reader [START_REF] Delgado | Don't throw away your printed books: A meta-analysis on the effects of reading media on reading comprehension[END_REF]. Thus, teaching effective task-dependent strategies is no less relevant in the online world as it is in the world of printed texts [START_REF] Kohnen | Can middle schoolers learn to read the Web like experts? Possibilities and limits of a strategy-based intervention[END_REF].

In the present study, we report the design and test of an instructional method to teach purposeful reading skills to elementary school children. We first review current theories of purposeful reading and evidence that mature readers adapt their reading behavior to the task at hand. We highlight the challenges of purposeful reading for developing readers. Then, we review studies that have attempted to train purposeful reading skills, with various levels of success. We draw from the benefits and limits of prior attempts to present a new framework for teaching purposeful reading skills in the elementary grades. In the later sections of the paper, we present the methods and results of an experiment involving the design and implementation of a teacher-led intervention based on this framework.

Challenges of purposeful reading in print and digital environments

As online reading becomes common practice in most parts of the world, readers find themselves with more opportunities to read diverse types of texts in a broader diversity of contexts [START_REF] Britt | Reading contexts, goals, and decisions: Text comprehension as a situated activity[END_REF]. Indeed, there has been an increased interest on the part of researchers for the situated, goal-driven nature of reading [START_REF] Mccrudden | Relevance and goal-focusing in text processing[END_REF]Snow, 2002;[START_REF] Vidal-Abarca | Individual differences for self-regulating taskoriented reading activities[END_REF]. In their MD-TRACE model, [START_REF] Rouet | Relevance processes in multiple document comprehension[END_REF] described the processes whereby readers engage with one or several text(s) in order to achieve a purpose.

Like prior descriptions of purposeful reading (e.g., the IPS-I model by [START_REF] Brand-Gruwel | A descriptive model of information problem solving while using internet[END_REF], MD-TRACE features a series of steps that unfold both sequentially and in interaction with each other. First, the reader understands the requirements of the instruction and builds a mental model of the task (a Task model, Step 1). The task model includes the expected task outcome and the actions to be performed (e.g., construct an answer to a question by gathering information from a set of documents), based on the reader's interpretation of any available contextual cue (e.g., instructions, stakes, resources, constraints). Once a task model has been generated, the reader starts searching for relevant information with the available information resource(s) (Step 2). They then selectively process and integrate information to come up with a task product (e.g., an answer to the search question; Step 3). Before giving a final answer, the reader may check that his or her task product corresponds to the question's requirements in terms of relevance and sufficiency (step 4). If not, the entire process gets repeated until the goal is achieved (or, sometimes, updated). Distinctive features of MD-TRACE are the role of goal formation and monitoring, and the cyclical nature of the activity, with several recycling loops corresponding to metacognitive processes.

Numerous studies have evidenced that mature readers strategically adjust their reading behavior as a function of the assigned task. For instance, [START_REF] Kaakinen | Task Effects on Eye Movements During Reading[END_REF] found that a proofreading task prompted different text scanning strategies, compared with a readingfor-understanding task. Similarly, [START_REF] Radach | The role of global top-down factors in local eye-movement control in reading[END_REF] asked undergraduates to answer questions (i.e., comprehension task) or to decide which of the four words presented was in a passage they had just read (i.e., word verification task). Participants fixated the text longer and more frequently when preparing to answer comprehension questions rather than word checking questions. In most educational systems, children are expected to acquire purposeful reading skills throughout primary education. Indeed, [START_REF] Kaakinen | The influence of a reading task on children's eye movements during reading[END_REF] asked 3 rd , 4 th and 6 th grade students, as well as adults, to read a text either to answer a specific question or to understand the text as a whole. Both children and adults showed different reading patterns for question answering than for global understanding. Nevertheless, older students and adults were more likely to backtrack to earlier portions of the text when reading to answer questions. In general, research suggests that older and/or more proficient readers are more prone to using purposeful reading strategies (e.g., Cataldo & Oakhill, 2000;[START_REF] Kobasigawa | Children's retrieval skills for school learning[END_REF][START_REF] Rouet | The acquisition of document search strategies in grade school students[END_REF].

Nevertheless, some tasks, for instance those that require finding and integrating information from different paragraphs, remain difficult, even for 15-year-old students (OECD, 2019).

Further research has attempted to identify the factors that could explain such difficulties.

Consistent with

Step 1 of the MD-TRACE model, readers' understanding of the task instructions is key to their reading outcomes. [START_REF] Vidal-Abarca | Individual differences for self-regulating taskoriented reading activities[END_REF] examined how skilled and less skilled 4 th and 5 th graders responded to questions containing inconsistencies (e.g., "When should treatment begin in order to cause (vs. to prevent) malaria?"). Skilled readers were more likely to report that the question was not correct than less skilled ones. These results are consistent with a study by [START_REF] Cerdán | Self-Generated Explanations on the Question Demands are not Always Helpful[END_REF] exploring 9 th graders ability to rephrase questions in their own words. Better comprehenders incorporated a higher number of transitional inferences indicating an effort to understand the questions, while poor comprehenders' reformulations contained many incomplete and erroneous ideas. As a result, poor comprehenders constructed incorrect and incomplete mental representations of the questions, resulting in poorer purposeful reading performance.

Developing readers' access to relevant parts of the text (i.e., Step 2 of the MD-TRACE model) can also be hindered by their limited use of text organizers. For instance, Rouet et al. (2011) found that 5 th and 7 th graders' selections in simulated Web menus were strongly influenced by shallow cues such as list order or capitalized keywords, irrespectful of their intrinsic relevance. In addition, [START_REF] Potocki | Children's visual scanning of textual documents: Effects of document organization, search goals and metatextual knowledge[END_REF] found that only half of 5 th graders used section and paragraph headers systematically to access relevant information, while others either read linearly or browsed randomly. Finally, Salmerón et al. (2018b) found that 7 th to 10 th grade students' ability to select of relevant pages increased with grade and was related to their comprehension outcomes.

Monitoring and evaluating the relevance and sufficiency of information (i.e., Step 3 of the MD-TRACE model) is also a complex facet of purposeful reading activities. [START_REF] Vidal-Abarca | Individual differences for self-regulating taskoriented reading activities[END_REF] observed that 4 th and 5 th graders did not systematically propose an answer to a comprehension question, even after reading a paragraph containing relevant information. Better comprehenders did so on two thirds of the occasions, as compared with less than half of the occasions for poor comprehenders. In addition, [START_REF] Cerdán | Selecting information to answer questions: Strategic individual differences when searching texts[END_REF] examined 14-year-old students' ability to reject distracting information contained in a text. Students were asked to read two texts and answer questions. Half of the questions had been manipulated to induce a misleading correspondence between the wording of the question and distracting information in the texts. Good comprehenders were more able to reject distracting information than poor comprehenders, who selected and processed the distracting information more frequently.

Finally, developing readers may struggle to assess the quality of reading outcomes (Step 4). In an early study, [START_REF] Kobasigawa | Children's retrieval skills for school learning[END_REF] asked 4 th and 5 th graders to assess another student's response to a purposeful reading assignment. In general, younger students did not spontaneously mention criteria such as the relevance or sufficiency of the information provided.

However, when explicitly prompted by the experimenter, 4 th graders were able to correctly indicate if the answer did not contain all the required information. This suggests that developing readers may have trouble monitoring the demands of a search question throughout the reading process (see also [START_REF] Cerdán | To answer questions from text, one has to understand what the question is asking: Differential effects of question aids as a function of comprehension skill[END_REF].

Thus, the processing steps involved in purposeful reading entail a number of challenges for developing readers, both in printed and in online reading situations. Nevertheless, reading for explicit purposes account for most daily reading activities of adolescents [START_REF] Lenhart | Teens, Social Media and Technology Overview[END_REF] and adults [START_REF] White | Reading-related literacy activities of american adults: Time spent, task types, and cognitive skills used[END_REF]. Learning to use text in the service of different tasks therefore represents a crucial instructional issue.

Teaching purposeful reading to developing readers

There is a long tradition of research aimed at teaching reading strategies using a variety of innovative instructional approaches (e.g., National Reading Panel, 2000;Palincsar & Brown, 1984;[START_REF] Paris | Informed strategies for learning: A program to improve children's reading awareness and comprehension[END_REF]. However, as [START_REF] Ng | Engaging readers in the twenty-first century: What we know and need to know more[END_REF] correctly pointed out, most of these interventions were conducted in the pre-Internet era and within the so-called Simple View of Reading framework (i.e., reading a text to form a broad understanding). Only a few studies have attempted to train elementary school students to address different types of reading tasks and purposes. These interventions can roughly be categorized in reference to the MD-TRACE model outlined above, depending on the type of process that was the focus of the intervention. Some studies have tested the effectiveness of "pre-search" activities to improve the understanding of the question and the construction of an appropriate task model (i.e., Step 1 in MD-TRACE). For example, [START_REF] Dreher | Fifth graders' search for information in a textbook[END_REF] asked 5 th grade students to reflect on keywords in a question, with beneficial effects on their document search strategies. More recently, [START_REF] Llorens | Assessing the comprehension of questions in taskoriented reading[END_REF] invited undergraduate students to identify the key information in the question and to explain how they would read in order to answer it, prior to engaging with the text. Compared to students in a control condition, those students gave significantly more correct answers. In addition, [START_REF] Cerdán | To answer questions from text, one has to understand what the question is asking: Differential effects of question aids as a function of comprehension skill[END_REF] asked 8 th grade students to read two texts and answer questions about them. For some of the questions, a paraphrase of the question was presented to the students before they started reading the texts. The presentation of paraphrases was beneficial to less-skilled readers. Finally, [START_REF] Ayroles | Do you know what you are reading for? Exploring the effects of a task model enhancement on fifth graders' purposeful reading[END_REF] asked 5 th graders to describe the information needed to answer a question prior to searching the answer in a text.

Compared with a control task, the pre-search elaboration resulted in a sharp increase in response correctness, although the examination of online reading patterns failed to show any speeding up of the search process, nor any increased focusing on relevant portions of the document.

Having students elaborate on the question arguably supports their construction of a more complete and robust task model, subsequently informing their reading strategies and leading to better outcomes.

In contrast with the evidence suggesting a link between patterns of visual inspection and document comprehension performance (e.g., [START_REF] Mason | Do fourth graders integrate text and picture in processing and learning from an illustrated science text? Evidence from eyemovement patterns[END_REF], there is a dearth of research on readers' use of so-called metatextual cues (e.g., keywords, headers) during purposeful reading in printed and online settings (i.e., steps 2 and 3 of the MD-TRACE model). [START_REF] Coutelet | Apprendre à chercher dans un texte : Effets d'un entraînement à 8 et 10 ans[END_REF] implemented a five-week classroom training program with one 30-minute session per week in 3 rd and 4 th -grade classes. The training tasks prompted students to think about their search goal and to consider metatextual cues such as keywords and headers. At an immediate post-test, trained students used more effective strategies compared to a control group. However, this effect did not significantly last after a delay. Interestingly however, among the trained students who were initially inconsistent in their use of a strategy (i.e., using sometimes linear, sometimes selective reading), 62.5% entirely gave up ineffective strategies at the delayed post-test. Assessing one's response quality (Step 4 of the MD-TRACE model) is considered a challenge for students, including at a post-secondary level [START_REF] Dunlosky | Overconfidence produces underachievement: Inaccurate self-evaluations undermine students' learning and retention[END_REF]., In an early study of purposeful reading, [START_REF] Dreher | Fifth graders' search for information in a textbook[END_REF] prompted 5 th graders to reflect on their acquisition of information prior to giving an answer to a search question. Compared to a control group, prompted students gave significantly more correct answers than students who completed the information-seeking activity without assistance. Likewise, Rouet et al. (2010) observed that secondary school students' selections in a simulated Web search results page improved after reading a short text on the topic, but the effect was limited to better comprehenders. Whether instructional procedures could foster students independent monitoring of response quality is, to our knowledge, an open question.

An instructional program to teach purposeful reading strategies

In total, there is some evidence that interventions focused on critical steps and challenges of purposeful reading can enhance grade school students' mastery of the respective skills. However, to date no intervention has attempted to provide a systematic program encompassing all the processes involved in purposeful reading. Regarding instructional approaches, purposeful reading relies on a mix of declarative and procedural knowledge (Britt et al., 2018). For instance, students need to learn both about the structure of texts, and how to engage or disengage from a text passage. Therefore, we developed a direct instruction program involving a combination of explanation and guided practice on each and every stage of the purposeful reading cycle. The program introduces the various subtasks involved in purposeful reading, with a combination of direct explanations followed by guided practice with feedback (see Table 1 for an overview; section 3.3.3 below and appendix A for details).

Table 1. Overview of the training program based on the MD-TRACE model of purposeful reading.

MD-TRACE component

Means of intervention Target declarative and procedural skills

Step 1. Construct a task model

Reflect on the key words of the questions and the nature of the information to be found.

Declarative aspect: analyze questions. Identify interrogatives and keywords.

Procedural aspect: highlight questions'

keywords and articulate nature of information to be found.

Step

Select relevant text

Use textual cues such as headers, paragraphs or keywords in the text.

Declarative aspect: define textual cues.

Procedural aspect: link keywords from the question with keywords from the textual clues to identify the location of relevant information.

Step 3. Extract and integrate

task-relevant information

Draw connections between the question and several portions of the text.

Declarative aspect: understand the differences between locate and integration questions.

Procedural aspect: identify relevant information in the text and integrate as needed

to construct an answer. Disengage and resume searching if no information is found.

Step 4.

Construct an answer

Rephrase text information, check answer with respect to question.

Declarative aspect: understand the elements that make up a correct answer.

Procedural aspect: compare the demands of the question and the proposed answer to check that they match. Recycle if they don't.

We subsequently tested the impact of the program in an experiment involving a series of teacher-led workshops in a pre-post-test design with an active control group.

Objectives and hypotheses

The objective of this study was to develop and test the effectiveness of a new training program based on an analytical approach of the steps and challenges involved in purposeful reading for 5 th graders. The program involved a set of instructional workshops, materials and tasks, developed in cooperation with a group of teachers. We tested the effectiveness of this teacher-led intervention against an active control group both on direct application tasks assessing each specific purposeful reading component, and on a more integrated (and unguided) purposeful reading task (i.e., a more naturalistic assignment, similar to what students typically encounter at school). We expected trained students to outperform controls on both purposeful reading component tasks (hypothesis 1) and on integrated purposeful reading task (hypothesis 2). We also explored whether potential progress was dependent on children's characteristics in terms of initial level in word reading, reading comprehension and metatextual knowledge.

Method

Population

Participants were nine teachers and 167 fifth graders from five primary schools located in a large semi-urban area of France. The participating teachers (6 female) had received their degree from a public teacher training institute and they had between five and 35 years of experience.

Only the 139 students who were present at both the pre and post-test sessions were considered in the analyses (mean age = 10.41). All the included students attended at least half of the training sessions and 81% attended all of them. Students participated as part of regular classroom activities led by their usual teachers. All the participants had French as their mother tongue.

Their reading level (i.e., written word identification and reading comprehension) as well as their strategy knowledge and skills were controlled for.

Study design

The program was designed collaboratively and approved by the local school authorities.

Throughout the experiment, data were collected by the teachers and transferred anonymously to the researchers following the guidelines of the European General Data Protection Regulation.

Teachers from a large school district that includes urban, semi-urban areas were informed about the study through in-service professional development events and direct Using a quasi-experimental design, participating classes were assigned to one of two subgroups balanced for students' overall level of comprehension as well as their geographic and socioeconomic status. One subgroup was initially assigned to the active control condition (i.e., the writing workshops; 4 classes from 13 to 22 students each, n = 78, mean age = 10.41), whereas the other was assigned to the experimental condition (i.e., the purposeful reading workshops; 6 classes from 11 to 23 students each, n = 89, mean age = 10.43). The initial plan was to later reverse the conditions, so that students in every participating class would take both the purposeful reading and the control writing prongs of the program. However, the study was interrupted due to the Covid-19 pandemic, which roughly coincided with the ending of the first phase. Therefore, the design was converted into a standard between-participant design. In addition, one of the teachers initially assigned to the control condition chose to withdraw from the study after a few sessions because of unrelated circumstances, reducing the size of the control group to 56 students (3 classes, mean age = 10.37).

Materials

Training programs

Two training programs relevant to the acquisition of language skills were developed: The Construct and evaluate the quality of the answer. Thus, the first four modules focused on each of the steps presented above (see Table 1). The last module contained purposeful reading tasks requiring the coordination of all these steps. An overview of the workshop contents and an example of student booklet are presented in appendices A and C, respectively.

Reading and Writing Training Program (control condition). Each module

of the reading and writing training program began with the reading of a text (180 words on average) followed by a series of tasks focusing on different syntactic and grammatical aspects (e.g., punctuation, sentence form and complements, morphology). The second workshop of each module consisted of a written production task in which the students had to rewrite a text by applying the elements worked on in the previous workshop (e.g., reproducing the structure of the text and using different punctuation marks appropriately). Thus, the control program was focused on written language skills, it featured activities that were new to the teachers and to the students, but it did not include any direct instruction of purposeful reading skills.

Pre and post-test measures.

Two types of tasks were administered at the pre-and post-tests. The first set of tasks ("purposeful reading component tasks") aimed to study whether students could reuse the skills specifically targeted by each training module (e.g., being able to build a task model, to access information efficiently and so forth) in tasks similar to those worked on during the workshops.

These measures allowed us to ensure that some kind of actual learning had occurred during the workshops. The second set of tasks ("integrated purposeful reading task") aimed to investigate whether students could reuse the targeted skills in a more "complete" purposeful reading task without any guidance on the different strategies to be used. This task consists in answering comprehension questions on a set of documents, without any question or instruction pointing to the strategies learned in the training modules.

Purposeful reading component tasks.

To test each specific component of the purposeful reading process, we created four tasks directly inspired by modules 1 to 4 of the purposeful reading program (Table 1). Each task was composed of four items with a preceding example to explain students how to complete the task. The first task ("Task model") focused on reflecting on the key words of questions and the nature of the information to be found. In this task, pupils had to underline and circle the key words of the question and then complete the generic sentence "Find _____ that corresponds to _________" (e.g., for the question "When was Salvador Dali born?", the expected answer was "Find a date that corresponds to the birth of Dali / when Dali was born"). The task included four items with for each, two slots to complete. The score corresponded to the number of slots correctly filled in by the student (maximum score = 8; α = .72). The second task ("Information access") focused on the use of headings as an aid to access relevant information. In this task, students were presented with a question followed by four potential title suggestions. In addition to having to identify the question's key words, students were asked to choose the title in which the answer to the question was most likely to be found (maximum score = 8; α = .65). In the third task ("Extract and integrate"), students had to answer a series of questions by looking for the answer in short texts of about 135 words, consisting of two paragraphs. To do so, they had to first underline the relevant information in the text (maximum score = 4) and then formulate a written answer based on this identified information (maximum score = 4) (maximum total score = 8; α = .82). Finally, in the fourth task ("Construct response"), students had to assess five proposed answers in terms of relevance and sufficiency with respect to a question. More specifically, they had to highlight the keywords of the question, to identify the correct answer and to explain why the other four proposals were incorrect (e.g., for the question "In which city was Coluche (a French humorist) born?", the answer "Coluche was born in Paris" is correct but the answer "Coluche was born in 1944" is incorrect because it indicates a date and not a location). The task included four items and students received a score from 0 to 6 for each item (i.e., 1 point for each correct relation plus 1 for the correct identification of the keywords of the question) (maximum total score = 24; α = .83). The dependent variables were the scores for each of the four tasks.

Note that although the 'purposeful reading component' task was similar to some of the practice tasks given to the experimental group, it did not contain items that had been previously presented to the students in either condition.

Integrated purposeful reading task.

A holistic, integrated task was administered to measure whether students could use the skills targeted in the Purposeful

Reading training program without guidance on how to use them. Indeed, the task did not contain any explicit indication of the strategy to be used and was therefore considered as a measure of students' ability to use their skills in a more naturalistic reading activity. It included a document consisting of several sections with subtitles and illustrations (see Figure 1). The document came with six questions involving different requirements: two were "locate questions", two were "comprehension questions" and two were "integration questions". For "locate questions", students had to find a single explicit piece of information located in a single paragraph of the document. For "comprehension questions", they had to make inferences to integrate several pieces of information from the same paragraph. Finally, for "integration questions", students had to compare or integrate several pieces of information from different paragraphs of the document. The text remained available while answering the questions. Students had a maximum of 10 minutes to answer the questions, i.e., a moderate time pressure based on informal pilot testing. The total score was the number of correct answers (maximum = 6; α = .62). The five tasks (four "purposeful reading component" and one "integrated purposeful reading")

were grouped together in a workbook. Three versions of the workbook with comparable content were created: one for the pre-test, one for the immediate post-test and one for the delayed posttest. The order of distribution of these workbook versions was balanced across classes.

Associated measures.

Different associated measures were administered in order to 1/ verify the homogeneity of our experimental and control groups at the pre-test, and 2/ examine the impact of these associated skills on the "purposeful reading component" and "integrated purposeful reading" measures and on the possible progress made by the students on these measures after the intervention.

Written word identification.

The standardized test "La Pipe et le Rat" [START_REF] Lefavrais | La Pipe et le Rat [Pipe and rat, reading test[END_REF]) was used to assess students' written word identification skills. In this task, students had a maximum of three minutes to silently read three pages of single words and to underline as many animal names as possible (around half of the words were animal names).

The dependent variable was the difference between the number of correctly underlined animal names and the number of incorrectly underlined words). The test manual did not include any reliability index for this measure. However, the scores obtained by our sample of children were within the norm for their chronological age (see [START_REF] Lefavrais | La Pipe et le Rat [Pipe and rat, reading test[END_REF].

Reading comprehension. The test "La Forme Noire" ([The Black Shape],

Maeder, 2010) was used to assess the students' level of reading comprehension. "La forme noire" is a standardized test used by psychologists and speech therapists to diagnose reading comprehension difficulties. It consists of a narrative text (522 words) followed by 15 multiplechoice comprehension questions. The text and questions are presented on separate sheets.

Students first read the text silently at their own pace and then answer the questions from memory, without the opportunity to reread the text. Performance is the number of questions correctly answered (maximum = 15; 𝜔 = .60).

Strategy knowledge.

A shortened version of the strategy knowledge questionnaire developed by Ayroles (2020) was used to assess students' strategy knowledge (i.e., metatextual knowledge) and control skills (i.e., planning, regulation, and evaluation) during a purposeful reading task. The questionnaire includes 10 items in which students are presented with a situation (for example: Your teacher asks you to read a text to answer a question. Before you start looking, what do you do most often to quickly find the answer in a text?) followed by a series of possible strategies. Students were asked to identify which strategy they think was most appropriate in this situation. The total score is the sum of the correct answers (maximum = 10, α = .60).

Procedure

The procedures for the administration of pre-and post-test measures, associated measures and intervention program are described in the following sections.

Pre and post-test measures.

Participants took the pre-and post-tests in whole classes, in sessions led by the researchers in cooperation with their usual teacher. Each session lasted for about an hour. Students first completed the "integrated purposeful reading" task (10 minutes maximum), then the first ("Task model") and second ("Information access") "purposeful reading component" tasks (20 minutes), and finally the third ("Extract and integrate") and fourth ("Construct response") "purposeful reading component" tasks (20 minutes). Students were granted a short break between each task. During the tasks, the experimenters and teacher made sure that all students were progressing normally. If necessary, they repeated the instructions to the students individually, using the example given for each task. A delayed post-test (5 weeks after the end of the intervention) was planned but could not take place due to the health crisis related to the COVID-19 pandemic.

Associated measures.

The associated measures were collected in a single whole-class 45-minute session, run by the experimenters in cooperation with the students' usual teacher. Students first completed the reading comprehension test (about 15 minutes), then the strategy knowledge questionnaire (also for about 15 minutes), and finally the written word identification test (5 minutes).

Training programs

The two training programs were implemented concurrently by the teachers in their classrooms at the rate of one module per week (each module being composed of 2 workshops of 45 minutes each), over a period of five weeks.

Each workshop followed the principles of explicit instruction [START_REF] Gauthier | Quelles sont les pédagogies efficaces ? Un état de la recherche[END_REF][START_REF] Gauthier | L'enseignement explicite[END_REF]: (1) presentation of the learning objective (5 minutes); (2) modelling: during which the teacher showed an example of how to carry out the exercise (5 minutes); (3) guided practice:

during which students worked in pairs and received corrective feedbacks from their teacher (10 minutes); (4) individual practice: during which students worked in autonomy and still received corrective feedbacks from their teacher (15 minutes); and (5) the final objectification phase in which students are expected to make explicit what was worked on and identify the essential skills and knowledge to be retained (5 minutes). The times indicated for each step were indicative for the teachers, as modifications could be made to adapt to the daily constraints of a class (bearing in mind that a 5-minute margin was already considered). Nevertheless, the researchers insisted that teachers respect the maximum time of 45 minutes per workshop, that they favor individual work, and that they interact strongly with the students to ensure that everyone understands and applies the instructional objective of the workshop.

Teachers received a one-day training session and were presented the content of the program and instructions to be implemented three to six weeks before the experiment began.

During the training session, the principles and organization of the intervention and a detailed example of one workshop session was presented for each of the training programs. Participating teachers had the opportunity to discuss the contents and activities to be presented both during the session, in the subsequent preparation period, and throughout the implementation.

Results

Informal examinations of logbooks and email communication indicated that the participating teachers complied with the content and organization of the training sessions, with the exception of one teacher who cancelled her participation due to a lack of time to prepare. The data from the corresponding class were excluded from the analyses.

Group homogeneity

To ensure group homogeneity at pre-test, we compared their mean scores on the associated measures (Table 2). The experimental and control groups did not differ significantly in terms of reading comprehension skills (t(1, 137) = -.688, p = .49) and strategy knowledge (t(1, 136) = 1.378, p = .17). A rather low level of strategy knowledge (rated out of 10) was noted for all participants. Finally, participants in the control group scored significantly better than those in the experimental group on the word identification test (U = 1863, p < .05). Both groups, however, were in the standard range for their grade level [START_REF] Lefavrais | La Pipe et le Rat [Pipe and rat, reading test[END_REF].

Effect of the intervention on the "purposeful reading component" tasks

Table 3 shows the descriptive statistics for each of the four tasks comprised in the measure of "purposeful reading component", at pre-and post-tests. Appendix B features the correlations between the four tasks for each condition.

To measure the effect of the intervention on each purposeful reading component, mixed model analyses were run using JASP software program with Time (pre-vs post-tests) and Group (experimental vs control) as fixed factors and participants and classes as random factors.

Students' scores in written word identification, reading comprehension and strategy knowledge were also entered in the models as well as their interactions with the Time factor. The dependent variables were the scores of the four tasks comprising the pre-and post-tests. In these analyses, significant Time*Group interaction is considered as evidence of the expected training effect (see Table 3). Concerning the first task ("Task model"), the effects of Time (F(1, 132.51) = 1.53, p = .22) and Group (F(1, 7.11) = 5.31, p = .054) were not significant. However, a significant Time * Group interaction was observed (F(1, 131.85) = 24.89, p ˂. 001). Post-hoc analyses did not reveal any significant difference between the experimental and control groups at pre-test (t(136) = .34, p = .74) but a significant difference at post-test (t(134) = -5.32, p < .001, Cohen's d = .93). There was also a significant difference between pre-and post-test in the experimental group, (t(78) = 8.15, p < .001, Cohen's d = .91) whereas no such difference was found in the control group (t(55) = -1.24, p =.22). As regards the associated measures, we observed significant main effects of Written word identification (F(1, 131.33) = 14.63, p < .001) and

Reading comprehension (F(1, 129.15) = 15.87, p = .02) but a non-significant effect of Strategy knowledge (F(1, 128.46) = 1.46, p = .22). However, none of these associated measures significantly interacted with the Time factor (F(1, 133.78) = .43, p =. 52; F(1, 131.97) = .17, p = .68; and F(1, 131.33) = .18, p = .68, respectively).

Concerning the second task ("Information access"), the effects of Group (F(1, 7.12) = 5.01, p = .06) and Time (F(1, 131.89) = .07, p = .89) were not significant. However, a significant interaction Time * Group was observed (F(1, 131.7) = 20.92, p ˂ .001). Post-hoc analyses did not reveal significant difference between the experimental and control groups at pre-test (t(137) = -.89, p = .37). However, at post-test, students in the experimental group outperformed the students in the control group (t(134) = -6.11, p ˂ .001, Cohen's d = 1.07). Finally, there was a significant difference between pre-and post-test in the experimental group, (t(79) = 4.43, p ˂ .001, Cohen's d = .50). The difference was also significant in the control group (t(55) = 2.31, p = .03) but in terms of performance loss (from M = 3.85; SD = 2.27 to M = 3.24; SD = 1.74).

Finally, we observed a significant main effect of Written word identification (F(1, 129. Concerning the third task ("Extract and integrate"), there was a non-significant effect of Group (F(1, 6.58) = .03, p =.87) and a non-significant effect of Time (F(1, 131.1) = 1.59, p = .22). Moreover, a non-significant interaction Time * Group was observed (F(1, 130.91) = 2.3, p = . 13). The main effects of Written word identification (F(1, 129.63) = 26.56, p < .001) and

Reading comprehension (F(1, 127.16) = 6.59, p = .01) were significant but not the effect of Strategy knowledge (F(1, 125.73) = 1.08, p = .3). However, the interaction between Strategy knowledge and Time was significant (F(1, 129.66) = 5.70, p = .02). The other interactions between Written words identification, Reading comprehension and the Time factor were not significant (F(1, 132.82) = 1.96, p = .16 and F(1, 130.56) = 2.12, p = .15 respectively).

Finally, concerning the fourth task ("Construct response"), the effects of Time (F(1, 133) = .62, p = .43) and Group (F(1, 6.74) = .27, p = . 62) were not significant. However, a significant interaction Time * Group was observed (F(1, 133) = 7.41, p < .01). Post-hoc analyses did not reveal significant difference between the experimental and control groups at pre-test, t(137) = .66, p = 51) nor at post-test (t(137) = -1.61, p = .11). However, there was significant difference between pre-and post-tests in the experimental group (t(82) = -4.58, p ˂ .001, Cohen's d = .50).

In contrary, no difference was found in the control group (t(55) = -.31, p = .76). Finally, the main effect of Written word identification was significant (F(1, 127.1) = 52.12, p < .001) but

Effect of the intervention on the integrated purposeful reading task

To measure the effect of the intervention on the integrated and unguided purposeful reading task, the same type of mixed model as for the "purposeful reading component tasks" analyses was run but with the score on the ecological purposeful reading task as the dependent variable.

The results did not reveal significant effects of Group (F(1, 6.14) = 2.54, p = .16), Time (F(1, 132.2) = .54, p = .46), nor a significant interaction between Group and Time (F(1, 132.01) = .76, p = .39). Thus, although the trend is consistent with our expectations (see

Discussion

The objective of this study was to design and test an instructional program for the teaching of purposeful reading skills to 5 th grade students. The program was designed following current theories of purposeful reading (Britt et al., 2018) and implemented by teachers in their usual classrooms following the principles of direct instruction. This program was compared to an active control condition in which teachers implemented a controlled training program focused on reading comprehension and writing production. The progress of the two groups of students were contrasted through their performance in various tasks.

Students in the experimental group improved their performance in the first ("Task model"), second ("Information access") and fourth ("Construct response") criterion tasks to a greater extent than students who took the active control program. In addition, effects sizes were medium to large, which is quite encouraging in the context of intervention studies [START_REF] Kraft | Interpreting effect sizes of education interventions[END_REF] and given the relatively short training period (7 hours over 5 weeks) and considering that the intervention program was delivered by the usual teachers and not the researchers (e.g., [START_REF] Jacob | When evidence is not enough: Findings from a randomized evaluation of Evidence-Based Literacy Instruction (EBLI)[END_REF][START_REF] James-Burdumy | Effectiveness of four supplemental reading comprehension interventions[END_REF]. Interestingly, we also observed that for these measures, students benefited from the program regardless of their initial level in written word identification, reading comprehension and strategy knowledge. Regarding the third task

("Extract and integrate information"), there was no change over time regardless of the condition. Regarding the integreated purposeful reading task, the observed pattern was consistent with our expectations but failed to yield a statistically reliable effect.

The results suggest that the "extract and integrate" task (Task 3) was less affected by training, and perhaps more dependent on students' general comprehension skills. Indeed, the task required students to answer location and integration questions without any further cue. For instance, the demands of the questions were not made explicit, nor were the participants explicitly invited to reflect on those demands. In other words, Task 3 was rather similar to the integrated task, which the intervention also failed to affect to a significant extent. The lack of a sizeable effect on more integrated tasks may be a consequence of the focused, segmented instructional approach used in the intervention. During the first four modules, the students in the experimental group were trained on independent skills. Thus, they may have missed an opportunity to use the skills in a more integrated way. [START_REF] Dreher | Fifth graders' search for information in a textbook[END_REF] also noted that children who had been taught information-seeking strategies failed to transfer their knowledge to varied tasks if they did not receive "systematic guided practice in the actual use of books" (p. 311). Primary school students may generally have "difficulty generalizing what they have learned and reusing it in another situation" (Coutelet & Rouet, 2004, p. 27, our translation). The final, "integrative" training module may not have been sufficient to let the students build a transferable skill. Indeed, as [START_REF] Coutelet | Apprendre à chercher dans un texte : Effets d'un entraînement à 8 et 10 ans[END_REF] rightly noted, "it is the accumulation of experiences that allows students to abstract the 'rule'" (p. 27). The lack of effect on the integrated task may also be explained by the large difference in format and complexity between the tasks presented in the last training module and the task administered as an integrated purposeful reading activity. Finally, unlike the practice sessions the assessment sessions involved a 10-minute time constraint. In sum, there may have been an excessive gap between the training and the evaluation tasks, which prevented students from generalizing the use of the component skills. As a partial compensation, the associated measures did not interact with condition or time, suggesting that despite its limited effectiveness the program was suitable to students with a range of related skills and knowledge.

The present study entails several limitations that limit the scope of our conclusions.

First, we compared the experimental condition with an active control condition in which students received an intervention focused on writing skills. after the conditions would have been switched across groups. However, the complete design could not be implemented due to a national lockdown period. Thus, we can only report shortterm outcomes of an incomplete design here. This might have reduced the opportunity to detect possible effects on the integrated task. Regarding this task, our study involved a single study task based on a set of documents, i.e., an admittedly limited assessment of students' skills.

Future studies should consider a broader set of measures, perhaps by including tasks directly generated by teachers as part of their classroom practices. Third, we were not able to implement a formal quality control procedure beyond our regular but informal communication with the participating teachers. Gathering systematic data about the actual implementation is important since there may be a gap between the resources provided, the instructions for use and their actual implementation (e.g., [START_REF] Horner | Resource leveraging to achieve large-scale implementation of effective educational practices[END_REF]. For instance, some of the teachers pointed out that the workshops were sometimes too dense and difficult to carry out in 45 minutes only.

However, we could not formally check that they had actually implemented all the different times relative to the explicit instruction approach [START_REF] Gauthier | Quelles sont les pédagogies efficaces ? Un état de la recherche[END_REF][START_REF] Gauthier | L'enseignement explicite[END_REF] or that they indeed provided appropriate feedback to their students. On-site observation and systematic debriefing may have helped build upon teacher experience but also provide information about quality of implementation that can affect the students' progress (e.g., [START_REF] Blase | Implementation science: Key concepts, themes, and evidence for practitioners in educational psychology[END_REF]. All these elements must be considered in further research into innovative teachers-led interventions.

In spite of these limitations, several instructional implications may be drawn from our results. First, the study yielded valid, usable educational resources to teach students the various skills underlying purposeful reading. In the present study, we focused on children at the end of primary school and, as a result, we focused on some aspects of the purposeful reading components, such as building an appropriate task model and accessing relevant information using textual organizers. However, such a purposeful reading training program would also benefit from being implemented later in the curriculum, e.g. in secondary school. For this age group, in addition to working with longer (and multiple) documents, we could consider targeting other types of purposeful reading skills, such as the ability to integrate information from multiple documents or to assess the reliability of information read (see for example [START_REF] Pérez | Fostering Teenagers' Assessment of Information Reliability: Effects of a Classroom Intervention focused on Critical Source Dimensions[END_REF]. Second, this study demonstrated the benefits of a simple intervention implemented by regular teachers in their usual classroom contexts. A mounting criticism of educational research is that innovative interventions were often led by researchers in highly controlled settings, with low replicability and a limited practical impact, if any [START_REF] Jacob | When evidence is not enough: Findings from a randomized evaluation of Evidence-Based Literacy Instruction (EBLI)[END_REF][START_REF] James-Burdumy | Effectiveness of four supplemental reading comprehension interventions[END_REF]. The present study brings encouraging results regarding the possibility to develop effective programs that require a minimal amount of professional development. As a result, this study goes beyond the simple validation of a pedagogical intervention but also puts in perspective the researcher-teacher interactions and the appropriation of research devices by the teachers (see [START_REF] Bressoux | Practice-based research: Une aporie et des espoirs[END_REF][START_REF] Bryk | AERA distinguished lecture: Accelerating how we learn to improve[END_REF], for discussions of this point). It seems that the initial training of the teachers, the many discussions between the teachers and the experimenters that followed, as well as the clear and systematic structure of the workshops, may have facilitated the teachers' appropriation of the intervention. In addition, informal teacher feedback suggested that, overall, the pupils enjoyed the content of the sessions and the homogeneous structure that enabled them to build capacity. Workshop 2: relate the question's key words to the type of information to be found Students underline the thematic words contained in the question, circle the interrogative word and complete the gap-fill sentence linking these 2 elements.

Organize your reading

Workshop 1: Identify the relevant title (avoiding false clues)

Students identify the title relevant to the question posed from a list. To do this, they must: 1. Underline the key words of the question 2. Circle the title they think is relevant.

Workshop 2: Rephrase the question to identify the relevant title Students identify the relevant title without a perfect match between the key words of the question and the relevant title.

To do this, they have to:

1. Identify the key words of the question by underlining them 2. Find synonyms and write them down 3. Circle the title they think relevant to find the answer Students identify the correct answer from a list of possible answers and, for incorrect answers, identify the error made. To do this, they have to: 1. Underline the key words of the question. 2. Circle the interrogative word 3. Indicate for each answer whether it is correct or not by linking it to an appropriate justification Become autonomous in the search for information Workshop 1: Find information in a text using headings Students complete an information retrieval task using the following steps: 1. Underline the key words of the question and circle the interrogative word 2. Circle the title(s) that seemed relevant 3. Read the selected paragraph(s) and underline the relevant information 4. Write a response 5. Reread the question and evaluate the quality of the answer Workshop 2: Find information in a text using headings Students complete an information retrieval task using the following steps: 1. Underline the key words of the question and circle the interrogative word 2. Circle the title(s) that seemed relevant 3. Read the selected paragraph(s) and underline the relevant information 4. Write a response 5. Reread the question and evaluate the quality of the answer

  contact. The two-pronged literacy training program outlined in section 3.3.1 was introduced as part of a one-day training workshop organized by the regional school authorities. Participation to the study was voluntary. Participating teachers were explained the goals, design, and methods of the study. They were presented the instructional approach and the type of explanations and tasks to be assigned to the students. During the implementation of the program, the researchers worked in close cooperation with the teachers. Teachers filled out a logbook indicating their progress and describing how the session went. Teachers and researchers also communicated informally over email.

"

  Purposeful Reading Training Program" focused on the four steps of purposeful reading, whereas the "Reading and Writing Training Program" focused on reading comprehension and writing from narrative texts. The latter program served only as an active control condition andwe had no specific hypothesis about its impact. Each program consisted of five modules, with each module involving two 45-minute workshops. Each workshop was composed of a workbook for students and a practical guide describing the structure and content of the workshops for teachers. The materials were sent to the teachers ahead of time and the researchers answered any clarification questions from teachers (see below, procedure).3.3.1.1. Purposeful Reading Training Program (experimental condition).The purposeful reading training program followed the different stages of purposeful reading described in the MD-TRACE model[START_REF] Rouet | Relevance processes in multiple document comprehension[END_REF]: (1) Construct a mental representation of the question -i.e., a task model, (2) Locate relevant passages among the available documents, using cues such as titles, (3) Extract and integrate information, and (4)

Figure 1 :

 1 Figure 1: Example of document presented during the integrated purposeful reading task.

  5) = 22.44, p < .001) but not Reading comprehension (F(1, 127.23) = .26, p = .61) nor Strategy knowledge (F(1, 125.69) = .03, p = .88). None of these associated measures interact significantly with the Time factor (F(1, 133.69) = .01, p = .91; F(1, 131.33) = .001, p = .97; and F(1, 130.4) = .01, p = .91, respectively).

  neither those of Reading comprehension(F(1, 126.62 = 1.5, p = .22) nor Strategy knowledge (F(1, 126.62) = 2.36, p = .13). None of the interactions between these associated measures and the Time factor were significant (F(1, 133) = 1.23, p = .27; F(1, 133) = 1.11, p = .29; and F(1, 133) = .25, p = .62 respectively).

  key words of the question Students circle the interrogative word and check the answer proposal that indicates the type of information requested by the question.

Table 2 . Means (sd) on associated measures for the two groups of children at pre-test.

 2

		Reading comprehension	Strategy knowledge	Written word identification
	Group	(range: 3-15)	(range: 0-9)	(range: 16-91)
	Experimental	8.70 (2.55)	3.98 (1.71)	50.02 (17.06)
	Control	8.39 (2.61)	4.41 (1.98)	57.61 (20.10)

Table 3 . Descriptive statistics in pre-and post-tests (sd in parentheses) and significance of the Time*Group interaction for the four "purposeful reading component" tasks.

 3

	Task	-test	Control	Experimental	Time*Group interaction
	1. Task model (range: 0-8)	Pre Post	4.55 (2.05) 4.14 (2.35)	4.45 (1.70) 5.99(1.70)	<.001
	2. Information access	Pre	3.85 (2.27)	4.17 (1.98)	<.001
	(range: 0-8)	Post	3.24 (1.74)	5.41 (2.22)
	3. Extract and integrate	Pre	4.24 (2.38)	3.77 (2.20)
					ns
	(range: 0-8)	Post	3.52 (2.04)	3.62 (2.27)
	4. Construct response	Pre	9.46 (7.01)	8.73 (5.97)	<.01
	(range: 0-24)	Post	9.70 (6.83)	12.2 (7.30)

Table 4

 4

	), the

Table 4 . Descriptive statistics in pre-and post-tests (sd in parentheses) and significance of the Time*Group interaction for the "integrated purposeful reading" task

 4

	Task	-test	Control	Experimental	Time*Group interaction
	Integrated task	Pre	2.92 (1.42)	2.93 (1.21)
	(range: 0-6)	Post	2.90 (1.26)	3.16 (1.30)	ns

  Our study demonstrates the value of training students, but not the value of specific instructional approach that was used. A more interesting comparison would be between two alternate approaches to training comprehension skills, to find out exactly what works and what does not. This sets the stage for future intervention studies. Second, the participating classes were expected to switch conditions and carry out the alternate training program after the first post-test. A second post-test was planned

  Students identify and integrate relevant information from multiple from several paragraphs. To do this, they have to: 1. Underline relevant information in the text. 2. Compare it to each other and to the question 3. Formulate an answer Students identify the correct answer from a list of possible answers and, for incorrect answers, identify what is wrong with them. To do this, they have to: 1. Underline the key words of the question. 2. Circle the interrogative word 3. Indicate for each answer whether it is correct or not by linking it to an appropriate justification Workshop 2: Assessing the adequacy of the response

		Workshop 2: Identify
		and integrate relevant
		information from
		multiple paragraphs
		Workshop 1: Evaluate
		answer accuracy
	Evaluate the
	quality of the
	response
		Workshop 1: Identify	Students identify relevant information, paying attention to
		relevant information,	false clues, to be able to formulate an answer. To do this,
		avoiding false clues, in	they have to:
		a single	1. Underline relevant information in the text
	Transform the	paragraph	2. Formulate a written response
	information
	read into a
	response

• In pairs (then alone) Instruction: Underline the theme words of the following questions: How many teeth are there in the jaw of a great white shark? Where did the solar plane land? Exercice 2

• In pairs (then alone) Instruction:

1. Circle the interrogative words in the following questions.

2. Check the suggested answer that indicates the type of information requested. How many teeth are there in the jaw of a great white shark?

A number A place A way A date

Where did the solar plane land? A quantity A period A place A cause

SUMMARY SHEET

To know what to look for, I need to identify the _____________________ ______________________ of the question and the _______________________ _________________________ to know what I need to find to answer it. The type of information to be found can be (cross out incorrect statements): a place, a name, an animal, a time, a date, a food, a number, a verb.

Purposeful reading: Module 1 -Workshop 2

Participant code:

Workbook

Exercise

• In pairs (then alone)

Instruction:

1. Underline the topic words and circle the interrogative words in the questions below.

2. Make the connection between these two items by completing the corresponding fill-inthe-blank sentences.

Where do Léa's grandparents live?


Nouaamane El Idrissi

Larbi Belachemi

Nicolas Merle

Philippe Zinck

Hamid Kaddami

Nouaamane El

Comprehensive preparation and catalytic activities of Co/TEMPO-cellulose nanocomposites: A promising green catalyst

Keywords: aerogel composite, cobalt nanoparticles, ion screening, green chemistry, cellulose, catalysis, recyclability. Highlights

published or not. The documents may come   L'archive ouverte pluridisciplinaire

Introduction:

The development of green, economic and highly active catalysts is at the heart of the research in catalysis. Heterogeneous catalysis is one of the most promising technology used in chemical reactions and environmental remediation. [START_REF] Munnik | Recent Developments in the Synthesis of Supported Catalysts[END_REF] [2] Metal and metal oxide nanoparticles (NPs) are emerging to be promising candidates due to their excellent catalytic activities for different organic chemical reactions [START_REF] Choo | Synergistic cascade catalysis by metal nanoparticles and Lewis acids in hydrogen autotransfer[END_REF]. However, their applications are limited because of their self-agglomeration in solution which reduces their catalytic performances. In addition, they are difficult to recover from the reaction medium. This is a supplementary challenge that limits their application in heterogeneous catalysis in non-supported structure. [START_REF] Mondal | Enhanced catalytic performance by copper nanoparticle-graphene based composite[END_REF]- [START_REF] Kaushik | Review: Nanocelluloses as versatile supports for metal nanoparticles and applications in catalysis[END_REF] The effective approach to overcome these problems is the immobilization of metal nanoparticles on different materials. [START_REF] Kaushik | Review: Nanocelluloses as versatile supports for metal nanoparticles and applications in catalysis[END_REF] In fact, supported heterogeneous catalysts is one of the major focuses of research in catalysis. The supports can be Metal oxides, Silica, Zeolites, Fibers, Ceramic materials, Pillared clays, and polymers notably [START_REF] Mondal | Cobalt nanoparticles as reusable catalysts for reduction of 4-nitrophenol under mild conditions[END_REF]- [START_REF] Munnik | Recent Developments in the Synthesis of Supported Catalysts[END_REF]. More recently, many research investigations have been directed towards the exploration of sustainable bio resources to be used as support of metallic particles catalysts. Being the most abundant, renewable, ecofriendly, biocompatible and biodegradable natural polymer, cellulose is widely used as a biomaterial support for catalytic systems due to its properties such as high specific area and strength promising good metallic nanoparticles integration. [START_REF] Gopiraman | Gold, silver and nickel nanoparticle anchored cellulose nanofiber composites as highly active catalysts for the rapid and selective reduction of nitrophenols in water[END_REF]- [START_REF] Zhang | Methods and applications of nanocellulose loaded with inorganic nanomaterials: A review[END_REF] On the other hand, important research attention has been paid towards the utilization of the first row transition metals, especially Ni, Co and Fe, as catalyst in organic synthesis. [START_REF] Mondal | Cobalt nanoparticles as reusable catalysts for reduction of 4-nitrophenol under mild conditions[END_REF], [START_REF] Rajesh | Recent advances in C(sp3)H bond carbonylation by first row transition metals[END_REF], [START_REF] Singh | Water oxidation catalysts based on abundant 1st row transition metals[END_REF] These metals represent advantageous alternative in organic synthesis compared to their equivalent noble metals of the second and third rows which are less abundant and more expensive. More specifically, the catalytic performances of Cobalt ions (either Co 2+ or Co 3+ ) as well as the less frequently used Co 0 , have been widely and extensively studied for, oxidations, C-H amination, Allylation, Alkenylation, etc. reactions. [START_REF] Hu | Cobalt-catalyzed sulfate radical-based advanced oxidation: A review on heterogeneous catalysts and applications[END_REF]- [START_REF] Kommagalla | Cobalt(II)-catalyzed CH functionalization using an N,N′-bidentate directing group[END_REF] Apart from the organic synthesis, various cobalt oxides based supported catalysts have been explored and extensively studied in high temperatures process, as active in methane catalysis decomposition (CDM) for the production carbon nanomaterials, for example. This enabled to reduce the CDM temperature to the range of 450-800°C [START_REF] Majewska | Low temperature one-step synthesis of cobalt nanowires encapsulated in carbon[END_REF], [START_REF] Pudukudy | Methane decomposition over Ni, Co and Fe based monometallic catalysts supported on sol gel derived SiO2 microflakes[END_REF]. On the other hand, this family of catalysts has been recently tested for water splitting and oxygen evolution or generation [START_REF] Liu | Conversion of electrodeposited Co(OH)2 to CoOOH and Co3O4, and comparison of their catalytic activity for the oxygen evolution reaction[END_REF]- [START_REF] Dou | Graphene-like holey Co3O4 nanosheets as a highly efficient catalyst for oxygen evolution reaction[END_REF].

Regarding the preparation of cobalt oxides (CoxOy), it worthy to emphasis that these different oxides are often synthesized by high temperature processes (T>400°C) involving oxidative/calcination of Co(OH)2, formerly prepared by alkaline treatment of Co 2+ salts (CoCl2 , CoNO2 or CoSO4, etc.). Other investigations have been conducted on the preparation of cobalt oxides by heating CO3Co in vacuum or in CO2, or by reduction of Co2O3 by NH3 or of Co3O4, by Carbon. Vice versa, Co3O4 can be obtained by the oxidation of CoO. [START_REF] Majewska | Low temperature one-step synthesis of cobalt nanowires encapsulated in carbon[END_REF]- [START_REF] Dou | Graphene-like holey Co3O4 nanosheets as a highly efficient catalyst for oxygen evolution reaction[END_REF] On the other hand the preparation of metallic Co 0 from Co 2+ ions based salts, such as CoSO4, can be achieved at room temperature by reduction reaction in presence of reducing agent such as hydrazine [START_REF] Zhao | Novel and efficient cobalt catalysts synthesized by one-step solution phase reduction for the conversion of biomass derived ethyl levulinate[END_REF], sodium borohydrid [START_REF] Wang | Cobalt-boron nanoparticles anchored on graphene as anode of lithium ion batteries[END_REF], etc.

In this work, we developed a novel, simple and eco-friendly biohybrid aerogels based on cellulose derivative (TEMPO oxidized cellulose) as support and cobalt Metallic (Co 0 ) particles as catalyst. The preparation of this biohybrid catalyst passes through the dispersion of Co 2+ ion salt (CoSO4) in the TEMPO-cellulose aerogel and its reduction in mild condition using NaBH4 as reducing agent. To the best of the authors knowledge, few studies are dedicated to the catalytic properties of cobalt supported on cellulose and the use of TEMPO-Cellulose as catalyst support for metal nanoparticles has never been reported as far as we know. In comparison to TEMPO-NFC, which production is energy demanding due to the mechanical defibrillation, the use of TEMPO-cellulose is a simple and novel way to endow cellulose with carboxylic groups that enhance the screen of Co 2+ cation to permit its reduction to Co 0 in presence of Borate anions. Compared to other nanocelluloses, this TEMPO-cellulose can be efficient to produce stable, efficient Co 0 supported catalyst. The morphology of this composite aerogel is characterized and its catalytic performances for the reduction of nitrofunctionalized molecules to amino-functionalized ones were tested.

Material and Methods

Chemicals and starting materials:

The rachis of date palm tree (Phoenix dactylifera L.) was used in this work as the original source of cellulose. Cellulose was extracted from the rachis following the procedure well described in our previous work. [START_REF] Bendahou | Physico-chemical characterization of palm from Phoenix Dactylifera-L, preparation of cellulose whiskers and natural rubber-based nanocomposites[END_REF] TEMPO

(

Preparation of the TEMPO-Cell

The rachis of date palm tree was used in this work as the original source of cellulose.

TEMPO mediated oxidation was performed following the procedure well described in our previous work [START_REF] Sbiai | TEMPO-mediated oxidation of lignocellulosic fibers from date palm leaves[END_REF], [START_REF] Benhamou | Control of size and viscoelastic properties of nanofibrillated cellulose from palm tree by varying the TEMPO-mediated oxidation time[END_REF]. About 2 g, i.e. 2.136 mmol of equivalent anhydroglucose unit (AGU) of cellulose, were suspended in water (200 mL) and sonicated with a Branson Sonifier for 5 min. TEMPO (32 mg, 0.065 mmol) and NaBr (0.636 g, 1.9 mmol) were added to the suspension. A certain amount of the NaOCl solution, corresponding to 40.5 mL was added drop wise to the cellulose suspension. The pH was adjusted at 10 by addition of a 0.1 M aqueous solution of HCl. The pH of the mixture was maintained to 10 at 4 °C by continuous adding of 0.1 M NaOH while stirring the suspension. After times ranging from 120 min, the oxidation was terminated by adding methanol (5 mL) and the pH was adjusted to 7 by adding 0.1 M HCl. The concentration of carboxylic acid groups has been calculated using conductimetric titration and the carboxylic content found is of 750 μmol/g; in agreement with our previous results [START_REF] Benhamou | Control of size and viscoelastic properties of nanofibrillated cellulose from palm tree by varying the TEMPO-mediated oxidation time[END_REF].

Preparation of TEMPO-Cell based aerogels and catalysts

Porous (Co/ TEMPO-Cell) aerogel composite was prepared by an environmentally friendly method. (CoSO4, 7H2O) was added to a dispersion of 1wt% of TEMPO-Cell in water (the amount of (CoSO4, 7H2O) was adjusted to obtain an aerogel composite (Co/ TEMPO-Cell) with 4wt% of Cobalt metal :1g of TEMPO-Cellulose, 0.19 g of (CoSO4, 7H2O) was added).

Then, sodium tetrahydroboride NaBH4 in distilled water was added. The amount of NaBH4 was calculated to have a stoechiometric ratio of 6M equivalent / Co. The dispersion turns immediately from pink to black colour. After that, the water was eliminated by lyophilisation after freezing the dispersion at -20°C during one night. The neat TEMPO-Cell aerogel was prepared lyophilisation method in the same conditions as for the supported catalyst.

The Co/TEMPO-Cell aerogel composite catalyst was prepared by the following reaction sequences which is described in the following S1 (Supporting data S1). The first step relates to the oxidation by NaOCl + NaBr + TEMPO mixture followed by treatment with cobalt sulphate CoSO4 in aqueous solution and reduction with NaBH4 (Supporting data S1).

Characterization techniques

Infrared spectra were recorded on a FT-IR Perkin-Elmer 1000 spectrometer collecting 32 scans from 400 to 4000 cm -1 . Transmission FTIR was performed on KBr based pellets prepared from grinded sample and KBr power. A separate background spectrum was collected and automatically subtracted from the raw spectrum for each specimen.

A Philips X'per wide angle X-ray diffractometer operated at 40 kv and 30 mA with a Nifiltered CuKα radiation was used to determine the crystallinity index of the specimens. X-ray diffractograms were recorded at 0.02° s -1 over a 2θ diffraction angle scan in the range 5-90°. XRD was performed, especially, to check the metallic structure of Co in the aerogel.

The model TESCAN -VEGA3, with accelerating voltage of 12.5 kV was used. A piece of aerogel was deposited on a SEM support and coated with a thin layer of carbon. EDX measurement was performed using AMETEK, EDAX-OCTANE PLUS.

The UV-vis spectra was used to study the kinetics of the reaction of reduction 4-Nitroaniline catalysed by TEMPO-Cell/Co catalyst. The spectra were taken at room temperature from 200 to 520 nm using a Shimadzu UV-vis spectrometer (UV-2450).

TEM

Transmission electron microscope FEI-Tecnai G2 operated at an accelerating voltage of 200 kV was used for the morphological observation.

TEM sample was prepared by depositing two to three drops of (1 mg/1 mL) Co/TEMPO-Cellulose suspensions on carbon-coated electron microscope grids and dried at ambient temperature.

XPS

XPS analyses were performed by a Kratos Axis Ultra DLD spectrometer with monochromatized Al Kalpha X-rays operating at 180 W (12 mA and 15 kV).

Catalytic Reduction of nitro-functionalized molecules

'' An aqueous solution of 0.

Kinetic studies by UV-Visible spectrometry

The kinetic monitoring of the reaction by UV-Visible spectrometry requires the establishment of a calibration curve to convert the absorbance into concentration of the studied solution.

Thus, we prepared solutions of NFM with different concentrations and we scanned the absorbance as a function of the wavelength (supplementary data S1-left). Monitoring the evolution of the intensity of the absorption band at 400 nm at the absorption maximum as a function of concentration allows us to obtain the calibration curve presented in S1-right. A straight line obtained by the origin and which therefore verifies the law of Beer Lambert. This calibration curve is used to study the kinetics of NFM reduction reaction.

Results and discussion

A. Aerogels Characterization

The morphology of Co/TEMPO-Cell was characterized by mean of scanning electron microscopy (SEM-EDX), FTIR spectroscopy, X-ray diffraction (XRD) and XPS.

Figure 1 shows the SEM pictures of pure TEMPO-Cell aerogel taken as reference and those of the Co/TEMPO-Cell aerogel composite with different magnifications. The optical photos of the aerogels are also presented to show their macroscopic aspect (figures 1-A and 1-B).

The SEM micrograph of cross section of the aerogel made of pure TEMPO-Cell aerogel shows the presence of micrometric fibers of 6-8 µm of diameter surrounded with films (figures 1-C and 1-E). These films are certainly formed of oxidized cellulose fibrils which were disintegrated from the bleached cellulose fibers during the TEMPO mediated oxidation process. In fact, it's well known that TEMPO mediated oxidation of cellulose fibers facilitated the dissociation of cellulose nanofibrils owing to the repulsive interactions developed between the carboxylate groups created [START_REF] Benhamou | Control of size and viscoelastic properties of nanofibrillated cellulose from palm tree by varying the TEMPO-mediated oxidation time[END_REF], [START_REF] Saito | Individualization of Nano-Sized Plant Cellulose Fibrils by Direct Surface Carboxylation Using TEMPO Catalyst under Neutral Conditions[END_REF]. These fibrils are then assembled and organized as a film during the freeze-drying process. In this structure the film ensure good connection and cohesion of the aerogel network which enables obtaining monolith aerogel [START_REF] Bendahou | Nanofibrillated cellulose-zeolites based new hybrid composites aerogels with super thermal insulating properties[END_REF]. Similar structure can be observed in SEM image of Co/TEMPO-Cell presented in Figures 1-H, 1-J and 1-L with the presence of small particles (diameter lower than 200 nm), homogeneously dispersed in the films (Figure 1-J). These particles are certainly composed of Co metal since they are absent in the pure TEMPO-Cell aerogel. The observation of the Co/TEMPO-Cell aerogel at higher magnifications (figures 1-J and 1-L) enabled to better distinguish these particles and to show that they are homogeneously dispersed in the films of cellulose. It is worthy noticing that bigger particles (diameter up to 2 µm) are also observed, and they are certainly formed by the aggregation of the nanometric ones.

EDX analyses (Figure 1-K and L) confirm that these particles are composed of cobalt. At that level the type of interaction between the TEMPO-cell and the metal particle is of high importance. SEM analyses cannot give information about this inquiry. However, in our approach the cobalt particles are fixed and stabilized by the hydrogen bonds to the TEMPO-Cell surface. It can easily be understood that the carboxylate groups at the TEMPO-Cell surface play an emulsifying effect to control the size and insure good dispersion of cobalt particles in the aerogel. The 2D-EDX elemental mapping enabled to show that the cobalt is homogeneously distributed in the composite aerogel (supporting data S2). As shown in the Figure 2, the cobalt nanoparticles are almost less than 4 nm in diameter and are well dispersed on the whole TEMPO-cell film. Their mean diameter (d) and standard deviation (σ) were estimated to be 2.4 and 0.8 nm, respectively. These particles are very small compared to those obtained in literature (see comparison in Table 1). This shows that, in comparison to the conventional NCC and NFC nanocelluloses, the TEMPO-cell has a pronounced emulsifying and stabilising effects, which enables the obtaining of very fine and well-dispersed metallic nanoparticles. The FTIR spectra of the Co/TEMPO-Cell composite aerogel and the pure TEMPO-Cell aerogel are presented in figure 4 and show characteristic vibration bands of the OH stretching at 4000-2995 cm -1 , the OH bending of adsorbed water at 1635 or 1638 cm -1 , the CH stretching at 2900 cm -1 , the HCH and OCH bending vibrations at 1430 cm -1 , the CH deformation vibration at 1375 cm -1 , the stretching vibration of C=O from the free COOH band near 1737 cm -1 , the C-OH bending mode at 668 cm -1 . Comparing the two spectra, it observed that the stretching vibration of C=O from the free COOH band at 1737 cm -1 disappears. Furthermore, the intensity of the band of C-OH bending mode at 668 cm -1 strongly increases. These observations confirm that the COOH and OH groups of cellulose are in interactions with cobalt nanoparticles, [START_REF] Karami | Cellulose supported bimetallic Fe-Cu nanoparticles: a magnetically recoverable nanocatalyst for quick reduction of nitroarenes to amines in water[END_REF], [START_REF] Heidari | Ag Nanoparticle/Nanofibrillated Cellulose Composite as an Effective and Green Catalyst for Reduction of 4-Nitrophenol[END_REF]. Several reports of the literature have shown that the reduction of cobalt(II) in homogeneous media with borohydride is very complicated. [START_REF] Lu | Cobalt precipitation by reduction with sodium borohydride[END_REF] To emphasis the effect of TEMPO-Cell on Co 0 metallic nanoparticle during the reduction with borohydride, a reduction of Co 2+ ions (CoSO4, 7H2O) in water (without TEMPO-Cell) using NaBH4 in the same conditions as for the preparation of borohydride Co/TEMPO-Cell has been performed (use of sodium NaBH4 in distilled water and the amount of NaBH4 was calculated to have a stoichiometric ratio of 6M equivalent/Co). We reported in Figure 5-A (lower spectrum) the XRD spectra of cobalt-based powder obtained. This spectrum shows that the resulting material is amorphous since no diffraction pick could be detected. In contrast, the XRD of Co/TEMPO-Cell composite, presented in Figure 5-B (upper spectrum),

shows a crystalline structure of Co 0 in its hexagonal polymorph, as indexed using Cobalt (JCPDS: 03-056-9722) crystal phase using High Score program. This enables to attribute the high intensity peaks observed at 2ϴ= 37.5 and 43.8 to the plans 301 and 220 of hexagonal metal structure of cobalt.

According to Suraj Gupta et al. [START_REF] Gupta | Cobalt-Boride: An efficient and robust electrocatalyst for Hydrogen Evolution Reaction[END_REF] and Y.D. Wang et al [START_REF] Wang | Exceptional electrochemical activities of amorphous Fe-B and Co-B alloy powders used as high capacity anode materials[END_REF] who prepared Cobalt based powder following similar procedure, this cobalt based powder is a Co-B amorphous materials.

The XPS analyses of this material show that the cobalt and bore metals exist in both elemental and oxidized state [START_REF] Gupta | Cobalt-Boride: An efficient and robust electrocatalyst for Hydrogen Evolution Reaction[END_REF]. In this structure, boron acts as the sacrificial agent in order to partially However, it's important to emphasise that TEMPO-Cell itself is not able to reduce the Co 2+ ions to Co 0 although it contains aldehyde and alcohol groups because of the lower value of the redox potential of the redox couple Co 2+ /Co 0 (-0.28 V) compared to that of redox couples aldehyde/alcohol (-0.2 V) and that of acid/aldehyde (-0.12 V) [START_REF]CRC Handbook of Chemistry and Physics[END_REF], [START_REF]CRC Handbook of Chemistry and Physics, 91st Edition -كتب Google[END_REF] But, it clearly appears that these organic groups present in TEMPO-Cell have an important role in specifically guiding the reduction of Co 2+ ions and the formation of Co 0 hexagonal. To this end, these hydroxyl, acid and aldehyde groups which are present at the surface of the TEMPO-oxidized cellulose matrix actively contribute to the selectivity of the catalytic reduction reaction for Co 2+ to Co 0 .

To further understand and confirm the above interpretation, hydrazine was used as reducing agent for the non-supported catalyst. The obtained metal consists of Co 0 with a cubic structure as revealed by XRD analysis presented in Fig. 5-A Para-aminoaniline is an aromatic diamine used in many application including the synthesis of Kevlar [START_REF] Finocchiaro | Synthesis and characterization of novel polyamides from new aromatic phosphonate diamine monomer[END_REF] and dyes matrices [START_REF] Park | Skin irritation and sensitization potential of oxidative hair dye substances evaluated with in vitro, in chemico and in silico test methods[END_REF], [START_REF] Dayan | Improved performance with molecular design of Ruthenium(II) complexes bearing diamine-based bidentate ligands as sensitizer for dye-sensitized solar cells (DSSC)[END_REF], while aminophenols are biologically active and are used in the pharmaceutical industry [START_REF] Mitchell | Aminophenols[END_REF].

The was accompanied by the apparition and the intensity increase of a new UV absorption band at 302 nm attributed to 4-AA. Surprisingly, even a very low amount of supported catalyst was found to be good enough to achieve 100% reduction of para-nitroaniline with a higher reaction rate However, with the non-supported Co catalyst, the reaction rate is lower and the reduction of 4-nitroaniline is achieved after 14 minutes (Figure 6-B).

The plot of (Ct/C0) as a function of reaction time, where C0 and Ct represent the concentrations at t = 0 and t of 4-NA in the reaction medium, are presented in figure 6-C shows a linear relationship for the kinetics with the two catalysts (Co/TEMPO-Cell composite and non-supported catalyst). This can be explained by the fact that the kinetic of this reaction is governed by the reagent contact with the catalytic surface which limits the number of molecules that can react at the same time.

The linear correlation between ln(Ct/C0) and time at 295 °K shows that the reduction of 4-NA, 2-NP and 4-NP by Co/TEMPO-Cell /NaBH4 follows the pseudo-first-order reaction kinetics.

The kinetic reaction rate constants (kapp) were estimated from the slope of the ln(Ct/C0) versus time liner curve. Pseudo-first order rate constant could be calculated by Langmuir-Hinshelwood equation [START_REF] Gopiraman | Gold, silver and nickel nanoparticle anchored cellulose nanofiber composites as highly active catalysts for the rapid and selective reduction of nitrophenols in water[END_REF].

Ln(Ct/C0) = ln(At/A0) = -k x t
where, k is the rate constant. C0 and Ct represents the initial concentration of 4-NA, 4-NP and 2-NP and the concentration at time t, respectively. A0 is the initial absorbance and At is the absorbance at any time t.

During the reaction, and notably in the beginning when the concentration of the substrate is much higher than the concentration of the catalyst, the catalyst surface is rapidly occupied by the substrate molecules and remains saturated during the reaction rending the reaction rate to appear constant throughout the reduction period. From these results, the apparent rate constant, kapp, was calculated as the slope of the linear plot of (Ct/C0) versus time. The turnover frequency (TOF, defined as the number of moles of 4-NA reduced per mole of catalyst per hour) could then be evaluated from kapp, to compare the catalytic performances of the two catalysts (Table 2). The TOF of Co/ TEMPO-Cell composite aerogel is 200 h -1 , while that of non-supported Co catalyst is 80 h -1 for 4-NA (Table 2). Similar trends are observed while studying the kinetic of reduction of 2-nitrophenol (2-NP) and 4-nitrophenol (4-NP). The results are presented in supporting data S4 and in Table 2. We clearly observe that the performances of Co/TEMPO-Cell composite aerogel for the reduction reaction of nitro group are higher in comparison to non-supported catalysts. This can be explained by the fact that the immobilization of particles on a cellulosic support increases surface area and makes cobalt metal nanoparticles more accessible to such nitrobenzene derivatives. The high specific area of cellulose and nanocellulose aerogels and their composites have been widely reported in literature; it has been shown that high values such 100 m 2 /g and 200 m 2 /g can be reached for these cellulosic aerogels [72][73][74]. Moreover, in the case of unsupported catalyst, the aggregation and agglomeration of particles significantly decreases their specific surface area, and limits their reagent accessibility.

Consequently, their reactivity is reduced even in the presence of an excess of NaBH4. The comparison of the two unsupported catalyst shows that the crystalline metallic form of cobalt is more effective than unsupported catalyst for this reaction.

Overall, the present Co/TEMPO-Cell catalyst shows greater efficiency for the catalysis of the reduction reaction of nitrobenzene derivatives when compared to previously reported systems (Table 2). We conclude that the TEMPO-oxidized cellulose plays a very important role in controlling the reduction reaction of cobalt(II) ions and orienting it chemo-selectively towards the cobalt nanoparticles which are immobilized on the surface of the matrix. The other possible reasons for the better catalytic activity could be (i) small size of the metallic cobalt nanoparticles, (ii) strong interaction between metallic cobalt nanoparticles and support owing to the presence of many carboxylic, aldehyde and hydroxyl groups on surface of the support and (iii) the high surface area of the composite aerogels. To the best of our knowledge, the present Co/TEMPO-Cell aerogel composite is an efficient catalyst for the reduction of nitroaromatic compounds reported to date in comparison to other metals supported catalyst.

The possible mechanism for the reduction of nitrophenols and nitroaniline has been previously reported. [START_REF] Naik | Short Communication[END_REF], [START_REF] Liu | A thermosensitive hydrogel carrier for nickel nanoparticles[END_REF] The complete reduction process occurs mainly on the surface of metallic cobalt NPs supported on the surface of TEMPO-oxidized cellulose. In the reduction of nitrophenols and nitroaniline, BH4 -acts as donor and the nitro group act as acceptor. In the first step, the nitrophenolate ion adsorbs on the surface of metallic cobalt catalyst and forms active hydrogen atoms. In the reduction process, the catalytic nanoparticles could act as an electronic relay system and speed up the electron transfer from BH4 -to nitro groups and the catalytic system subsequently gives aminophenols and aminoaniline. The number of moles of 4-NA reduced per mole of metal catalyst per hour (turnover frequency, TOF) values was 154 and 171 h -1 for 4-NA and 2-NP, respectively. This TOF difference between 4-NP and 2-NP is most likely due to the existence of more electronic effect on 2-NP which makes it relatively more ease for the substrate to be adopted on the metallic cobalt nanoparticles. On the other hand, the intramolecular hydrogen bond which increases the formation and adsorption of phenolate on metallic nanoparticles. The higher TOF value of 4-NA 200 h -1 is most likely due to the high capacity of the nitrogen atom of the amino group to adsorb onto nanoparticles of cobalt.

C. Recyclability Study

Recycling and reusability of heterogeneous catalysts is one of the desirable aspects in commercial processes. In order to examine this issue, reusability of Co/TEMPO-Cell aerogel composite was examined towards NaBH4 reduction of the three nitrophenol derivatives (4-NA, 4-NP and 2-NP). After completion of the reactions, the composite catalyst was separated from the reaction mixture by simple filtration, washed with EtOH and then dried under air atmosphere for additional using at the next runs. The obtained results show that Co/TEMPO-Cell aerogel composite was reused for 11 consecutive cycles without significant loss of its catalytic activity (Figure 6-D) for the reduction of 4-NA and in supporting data S4 for the reduction of 4-NP and 2-NP.

Conclusion

In this study, Co/TEMPO-Cellulose aerogel composite was prepared by simple insitu

  5 g/L NFM (nitro-functionalized molecule: 4-nitroaniline, 4-Nitrophenol or 2-Nitrophenol) is prepared, which correspond to 3,5 mM solution of NFM. For each reaction test, a 10 mL of this solution of NFM in water was used, in which an amount corresponding to 10 equivalents of NaBH4 vas added. An amount of aerogel catalyst Co/TEMPO-Cell, respecting the ration N(Co)/N(NFM)=0.05 was then added. The mixture is mildly stirred at room temperature. In these condition Molar ratio of NaBH4 / NFM / Catalyst is 1000 / 100 / 5 ''.

A:

  Optic photo of pure TEMPO-Cell aerogel B : Optic photo of Co/ TEMPO-Cell aerogel C: Pure TEMPO-Cell aerogel : Magnification of 500 D: Co/ TEMPO-Cell aerogel : Magnification of 500 E: Pure TEMPO-Cell aerogel : Magnification of 2000 F: Co/ TEMPO-Cell aerogel : Magnification of 2000 G: Pure TEMPO-Cell aerogel : Magnification of 10000 H: Co/ TEMPO-Cell aerogel : Magnification of 10000 I: Pure TEMPO-Cell aerogel : Magnification of 20000 J: Co/ TEMPO-Cell aerogel : Magnification of 20000 K: EDX of Pure TEMPO-Cell aerogel L: EDX of Co/ TEMPO-Cell aerogel

Figure 1 :Figure 2 :

 12 Figure 1: Optical, MEB and EDX characterizations of the TEMPO-Cell and Co/

Figure 3 :

 3 Figure 3: XPS of A: Co/TEMPO-Cell B: synthesized CoB

BFigure 3 -

 3 Figure 3-B shows different XPS peaks compared to the pure metal. The amorphous CoB

Figure 4 :

 4 Figure 4: FTIR spectra of TEMPO-Cell and Co/ TEMPO-Cell composite aerogel.

protect

  Co from oxidation. This clearly indicates the strong interaction between Co and B in CoB and Co2B boride cobalt. At this stage, it's interesting to compare the reactivity of Co 2+ toward the reductive action of sodium borohydride in presence and in absence of TEMPO-oxidized cellulose. It's clear that cellulose has an influence in the orientation of the catalytic reduction reaction and the development of Co hexagonal metallic structure instead of Co-B and Co2B amorphous cobalt borides components. It's clear that the strong interaction between B and Co in Co-B component prevent the growth of crystalline structure of metallic Co (Hexagonal or Cubic allomorphs). In presence TEMPO-Cell, the interactions between the hydroxyl, aldehyde and carboxylate groups of TEMPO-Cell and the cobalt (II) and BH4 -ions causes a high chemoselectivity which directs the reduction reaction towards the formation of cobalt (0) nanoparticles exclusively by screening the Co 2+ ions and preventing the formation of CoB and Co2B which are usually observed in this type of reduction observed in the absence of TEMPO-oxidized cellulose.

Figure 5 :

 5 Figure 5: XRD analyses; A: XRD of the powders obtained by the reduction of CoSO4

Figure 6 :

 6 Figure 6: A and B : UV-Vis spectra for the reduction of 4-NA with NaBH4 in aqueous

Table 2 :

 2 Comparison of the reducing ability of Co/TEMPO-Cell aerogel composite in reduction of nitro-functionalized molecule (NFM) with other reported systems *CTAB : hexadecyltrimethyl ammonium bromide ** P(2-acrylamido-2-methyl-1-propansulfonic acid)-Ni nanoparticles hydrogel

Figure 1 :Figure 2 :

 12 Figure 1: Optical, MEB and EDX characterizations of the TEMPO-Cell and Co/ TEMPO-

Figure 3 :

 3 Figure 3: XPS of A: Co/TEMPO-Cell, B: synthesized CoB;

Figure 4 :

 4 Figure 4: FTIR spectra of CNF and Co/ TEMPO-Cell composite aerogel.

Figure 5 :Figure 6 :

 56 Figure 5: DRX analyses; A: XRD of the powders obtained by the reduction of CoSO4 using

Table 1 : Comparison of the metal nanoparticles size with other reported systems

 1

	Metal	Nanoparticles size (nm)	Precursor	synthesis method	Support	Application	Reference
	Au	15.6	HAuCl4	reduction by NFC	NFC	Catalyst	Alle and al. [41]
	Au	12-19	HAuCl4	reduction by NCC	NCC	glucose detection	Alle and al. [42]
	Au Ag	18-25 6-35	HAuCl4, AgNO3	reduction by ascorbic acid	NCC	Catalytic reduction of nitrophenol	Eisa and al. [9]
	Au Pd	15-30 20	HAuCl4 PdCl3	reduction by dialdehyde NFC	NFC	suzuki coupling reaction	Zhang and al. [43]
	Ag	10-20	AgNO3	Sodium citrate	CMC/NCC	Antibacterial properties	Yunqing and al. [44]
						sensors,
	Ag	10-100	AgNO3	reduction by NaBH4	NCC	catalysts, and conductive	Dafne and al. [45]
						material
	Pd	6	PdCl2	NaBH4	NFC	Catalyst	Meng and a., [46]
						Catalytic
	Cu	14.65	CuSO4	reduction by hydrazine	NCC	oxidation of sulfides and	Dutta et al. [47]
						alcohols
	Cu	7	CuSO4	reduction by NaBH4	NCC	C-N coupling reactions	Goswami and al. [48]
	Co	2.4	CoSO4	reduction by NaBH4	TEMPO-Cellulose	Catalytic reactions reduction	This work

Table 1 :

 1 Comparison of the metal nanoparticles size with other reported systems

Table 2: Comparison of the reducing ability of Co/TEMPO-Cell aerogel composite in reduction of nitro-functionalized molecule (NFM) with other reported systems

Acknowledgements