Structured and multifunctional nanomaterials based on chitosan : syntheses and applications

L'utilisation des huiles de pétrole et autres ressources carbonées non renouvelables génèrent une quantité considérable de déchets avec un impact négatif sur l'environnement et la santé publique. Par conséquent, la recherche de matériaux biosourcés afin de substituer les matériaux pétrosourcés s'est intensifiée ces dernières années. Dans cette thèse, nous avons étudier les propriétés du chitosane, un polysaccharide aminocarbohydrate obtenu par désacétylation de la chitine, pour structurer la matière à l'échelle nanométrique.Nous présentons une nouvelle méthode simple permettant d'incorporer des nano-objets endogènes dans des films à base de polysaccharides. La chimie supramoléculaire basée sur l'auto-assemblage de polysaccharides associé à la polymérisation sol-gel a ainsi permis de convertir des précurseurs solubles de chitosane et d'alcoolates métalliques en films constitués de clusters d'oxyde métallique nanostructurés et de chitosane. Une large gamme d'oxydes métalliques simples, binaires et ternaires a été incorporée avec succès dans les bioplastiques. L'utilisation multiforme de ces films a été démontrée en les transformant sous traitement thermique doux en composites oxyde métallique - chitosane partiellement oxydés ou en les désintégrant dans des conditions aqueuses pour produire des nanoparticules d'oxyde métallique stables et dispersées dans l'eau. L'utilité de ces films fonctionnels a été démontrée comme agents antimicrobiens.Nous avons également démontré un effet de structuration intéressant de ces polysaccharides lors de la croissance de polymères de coordination poreux. Nous avons étudié la croissance de phases HKUST-1 et ZIF-8 dans une solution colloïdale de biopolymères de chitosane de poids moléculaire différents et dans diverses conditions de réaction. En plus de préparer des hybrides nanostructurés polysaccharide-MOF à porosité hiérarchique, nous avons également réussi à façonner le corps du matériau sous forme de films flexibles, de monolithes poreux et de microsphères autoportantes. L'évaluation de l'élimination du colorant Rouge Congo dans l'eau a révélé que les nanohybrides chitosane-MOF à porosité ouverte surpassent les phases pures (MOF microporeux et chitosane).Les propriétés chélatantes du chitosane en font un précurseur approprié pour l'immobilisation d'espèces métalliques dans une matrice carbonée. Des composites métal-carbone dérivés du chitosane ont été préparés. Des propriétés physico-chimiques attractives, à savoir une surface spécifique élevée, une dispersion métallique uniforme, et l'existence d'espèces azotées actives ont été obtenues. En raison de l'effet de structuration du chitosane envers les précurseurs d'alcoolate de métal , un ensemble d'oxydes métalliques cristallins comprenant des clusters de dioxyde de titane, d'oxyde de germanium et d'oxyde de fer ont été obtenus in situ dans un squelette de carbone dopé à l’azoté formé.Finalement, nous avons étudié la préparation de catalyseurs pour l'hydrogénation de composés insaturés tels que les quinoléines, les alcynes et les alcènes. Des nanoparticules de cuivre supportées sur carbone dopé à l’azote ont été préparées par pyrolyse de mélange généré à partir du nitrate de cuivre (II) dans une solution aqueuse de mélamine et de chitosane. L'EDTA a également été introduit pour améliorer la dispersion des nanoparticules de Cu lors de la synthèse. Le catalyseur optimal CuNC-1-700 présente de bonnes performances catalytiques pour les réactions étudiées.The use of petroleum oils and other non-renewable carbon resources generates a considerable amount of waste, with a negative impact on the environment and health. As a result, the search for bio-based materials to replace petroleum-based materials has grown in the recent years. In this thesis, we studied the properties of chitosan, an aminocarbohydrate polysaccharide obtained by deacetylation of chitin, to structure the matter at the nanometric scale.We present a new and simple method for incorporating endogenous nano-objects into polysaccharide films. Supramolecular chemistry based on self-assembly of polysaccharides associated with sol-gel polymerization has thus made it possible to convert soluble precursors of chitosan and metal alkoxides into films consisting of nanostructured metal oxide clusters and chitosan. A wide range of simple, binary and ternary metal oxides have been successfully incorporated into bioplastics. The multifaceted use of these films has been demonstrated by transforming them under soft heat treatment into partially oxidized metal oxide-chitosan composites or by disolving them in aqueous conditions to produce stable, water dispersed metal oxide nanoparticles. The usefulness of these functional films has been demonstrated as antimicrobial material.We have also demonstrated an interesting structuring effect of these polysaccharides during the growth of porous coordination polymers. We studied the growth of HKUST-1 and ZIF-8 phases in a colloidal solution of chitosan biopolymers of different molecular weight and under various reaction conditions. In addition to preparing nanostructured polysaccharide-MOF hybrids with hierarchical porosity, we also succeeded in shaping the materials into flexible films, porous monoliths and self-supporting microspheres. Evaluation of the removal of Congo Red dye in water revealed that the chitosan-MOF hybrids outperform the pure phases (microporous MOF and chitosan).The chelating properties of chitosan make it a suitable precursor for the immobilization of metallic species in a carbonaceous matrix. Metal-carbon composites derived from chitosan have been prepared. Attractive physico-chemical properties, among high specific surface area, uniform metal dispersion, and existence of active nitrogen species, have been obtained. Due to the structuring effect of chitosan towards metal alkoxide precursors, a set of crystalline metal oxides comprising clusters of titanium dioxide, germanium oxide and iron oxide were obtained in situ in a nitrogen-doped carbon skeleton formed.Finally, we studied the preparation of catalysts for the hydrogenation of unsaturated compounds such as quinolines, alkynes and alkenes. Copper nanoparticles supported on nitrogen-doped carbon were prepared by pyrolysis of a mixture generated from copper (II) nitrate in an aqueous solution of melamine and chitosan. EDTA was also introduced to improve the dispersion of Cu nanoparticles during synthesis. The optimal catalyst CuNC-1-700 shows good catalytic performance for the studied reactions

Detecting Botclouds at Large Scale: A Decentralized and Robust Detection Method for Multi-Tenant Virtualized Environments

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Cu nanoparticles embedded on reticular chitosan-derived N-doped carbon: Application to the catalytic hydrogenation of alkenes, alkynes and N-heteroarenes

International audienceApplying biomass-waste as catalysts and catalytic supports is gaining a tremendous interest owing to its expected outcomes in terms of cost effectiveness and sustainability. In this context, we herein disclose a straightforward encapsulation of nanosized copper on hierarchically porous, biomass-derived nitrogen-containing carbon framework. Our approach uses chitosan - derived from the marine shell-fish wastes - as a cheap, sustainable carbon and nitrogen source, melamine as nitrogen provider and ethylenediaminetetraacetic acid as a cross-linker to induce the reticular network, much suitable for restricting the growth of the metal seeds. The resulting copper grown on nitrogen-doped carbon, bearing relatively large surface area (106 m2·g−1) and a large group of well-dispersed Cu nanoparticles (average of 2 nm) even with high Cu loading (41 wt%), exhibits catalytic activity for the hydrogenation of unsaturated double and triple carbon-carbon bonds and heteroaryles. This sustainable design of catalyst, using affordable copper and cheap biowaste, could discard palladium and other expensive elements loaded on tedious synthetic supports from the library of heterogeneous solids intended for fine chemical synthesis

Hierarchically porous MOF-biopolymer beads for CO2 storage

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MOF/chitosan composites for the capture of gaseous iodine

International audienceMetal-organic frameworks (MOF) is an emerging class of crystalline and porous materials. Their structure results from the combination of metal clusters (or ions) with multitopic organic linkers. By changing the metal or the linker, or by adding organic functionalities to the linker, the physicochemical properties of the MOF can be tailored for specific applications. For instance, iodine-131 is a major fission by-product which can increase the incidence of thyroid cancers. Following a nuclear meltdown, venting is conducted to avoid overpressurization. The vented steam, containing radionuclides such as 131I2, passes through a filtered containment venting system to capture the contaminants. Typically, a fixed bed of silver-doped ZSM-5 zeolite is used. However, several limitations remain due to the small pore aperture of the zeolite (0.55 nm), hardly accommodating bulky iodine derivatives, and the competitive adsorption of contaminants (mainly CO). Hence adsorbents more specific towards I2 and its derivatives, presenting larger pores and/or higher iodine capture capacity, remain desired.In particular, the UiO-66 MOF presents a good stability against water, a high adsorption capacity, and larger pore sizes (0.8 to 1.1 nm). By adding amino moieties on the terephthalate linker, one can obtain UiO-66_NH2, an adsorbent with high binding energy towards electro-acceptor species such as I2. Recently, our group applied severe nuclear accidental conditions to this MOF, previously shaped as binderless granules, showing high retention of 131I2 and preserved physicochemical properties.[1] In a subsequent step, we studied the preparation of UiO-66_NH2-based extrudates and granules with improved mechanical properties by adding biopolymers. With lesser than 5 wt.% of chitosan, the textural properties of the resulting composites are barely affected - in line with the chitosan loading, and as-prepared materials present both high adsorption capacity towards iodine (see Figure 1.A-B) and a significantly improved mechanical resistance.[2] Still, shifting from a fixed bed of powder to a fixed bed of granules has consequences over the adsorption kinetics, with gaseous I2 diffusing in-between the granules. Hence, in a next step, we prepared composite films with up to 60 wt.% of UiO-66_NH2 MOF (Figure 1.C). By doing so, the adsorption equilibrium was reached within 24 h as per the MOF powder. Moreover, the total quantity of I2 adsorbed correspond to the loading of the MOF, meaning that up to 40 wt.% of chitosan, the porosity of the MOF remains fully accessible. The main results and perspectives of these works will be discussed

Shaping MOF oxime oxidation catalysts as three-dimensional porous aerogels through structure-directing growth inside chitosan microspheres

Metal-organic frameworks stand as unique building blocks, bridging the gap between coordination chemistry and materials science. While significant advances have been made in their design, current efforts focus on expanding their pore size above the microporous regime and on their shaping into well suitable end use devices. For such a purpose, we herein explored the use of chitosan hydrogel microspheres as a mold to grow an extended network of MOFs, followed by CO-supercritical drying to generate three-dimensional polysaccharide nanofibrils embedding entangled MOF nanoclusters. This strategy was found to be highly versatile, and allows for shaping HKUST-1, ZIF-8, ZIF-67 and Fe-BTC inside chitosan microspheres. The resulting lightweight aerogels display excellent activity for oxime oxidation, with HKUST-1 loaded on chitosan beads standing as the most promising. The virtues of supercritical drying were substantiated by comparing the catalytic activity of these aerogels with their xerogel analogues as well as pristine HKUST-1. Interestingly, moreover, the configuration of MOFs in chitosan beads precludes the metal from leaching and allows easy recovery of the catalyst from the medium and its possible recycling.NH thanks UEMF and UPV for an Erasmus+ 2019-1-ES01-KA107-062073 Scholarship. AEK thanks UEMF for funding. Partenariat Hubert Curien – Toubkal (project no. 18/70) is acknowledged for supporting and partially funding this work. Chevreul Institute (FR 2638), Ministère de l'Enseignement Supérieur et de la Recherche, Région Hauts-de-France and FEDER are acknowledged for funding. The authors are also thankful for the technical support from Lille University: Martine Trentesaux and Pardis Simon for the XPS analysis, Olivier Gardoll for the TGA analysis, Laurence Burylo for the XRD experiments, and Jeremy Dhainaut for the mechanical tests, and Ridvan Yildiz from LMCPA, Hauts de France Polytechnic University for mercury intrusion

Hierarchically Porous ZIF-67/Chitosan Beads with High Surface Area and Strengthened Mechanical Properties: Application to CO2 Storage

International audienceIn this work, zeolitic imidazolate framework-67 (ZIF-67)/chitosan composite beads were prepared by immersing chitosan beads incorporating cobalt (hydr)oxide into a solution containing the organic linker (2-methylimidazole). Compared to the conventional preparation protocols for metal-organic framework/polymer beads, the in-situ growth approach developed herein allows obtaining higher surface area with the shaped composites, up to 1200 m2/g for ZIF-67/CS2:1. The CO2 adsorption capacity of these ZIF-67/chitosan beads was investigated and reached 1.21 mmol/g at 273 K, which represents almost 100% of the adsorption capacity of pure ZIF-67, in line with the preserved surface area despite the incorporation of the 19% of additives included. Importantly, the ZIF-67/chitosan beads with an average bulk (crush) strength of 1.57 N could be easily regenerated, with a retained efficiency above 97% after 6 cycles. Furthermore, a possible mechanism for CO2 adsorption is discussed

Enhanced Gas Adsorption in HKUST-1@Chitosan Aerogels, Cryogels, and Xerogels : An Evaluation Study

International audienceThis study investigates the use of chitosan hydrogel microspheres as a template for growing an extended network of MOF-type HKUST-1. Different drying methods (supercritical CO2, freeze-drying, and vacuum drying) were used to generate three-dimensional polysaccharide nanofibrils embedding MOF nanoclusters. The resulting HKUST-1@Chitosan beads exhibit uniform and stable loadings of HKUST-1 and were used for the adsorption of CO2, CH4, Xe, and Kr. The maximum adsorption capacity of CO2 was found to be 1.98 mmol·g–1 at 298 K and 1 bar, which is significantly higher than those of most MOF-based composite materials. Based on Henry’s constants, thus-prepared HKUST-1@CS beads also exhibit fair selectivity for CO2 over CH4 and Xe over Kr, making them promising candidates for capture and separation applications

Glassy-like Metal Oxide Particles Embedded on Micrometer Thicker Alginate Films as Promising Wound Healing Nanomaterials

Micrometer-thicker, biologically responsive nanocomposite films were prepared starting from alginate-metal alkoxide colloidal solution followed by sol-gel chemistry and solvent removal through evaporation-induced assembly. The disclosed approach is straightforward and highly versatile, allowing the entrapment and growth of a set of glassy-like metal oxide within the network of alginate and their shaping as crake-free transparent and flexible films. Immersing these films in aqueous medium triggers alginate solubilization, and affords water-soluble metal oxides wrapped in a biocompatible carbohydrate framework. Biological activity of the nano-composites films was also studied including their hemolytic activity, methemoglobin, prothrombin, and thrombine time. The effect of the films on fibroblasts and keratinocytes of human skin was also investigated with a special emphasis on the role played by the incorporated metal oxide. This comparative study sheds light on the crucial biological response of the ceramic phase embedded inside of the films, with titanium dioxide being the most promising for wound healing purposes

Polysaccharide templated biomimetic growth of hierarchically porous metal-organic frameworks

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