Cyclodextrin-based systems for the stabilization of metallic(0) nanoparticles and their versatile applications in catalysis

International audienceIn order to better respond to environmental standards, the development of metal nanoparticles using green approaches has exponentially grown for the last decade. Cyclodextrins, which are cyclic oligosaccharides composed of 6(α), 7(β) or 8(γ) glucopyranose units, have appeared to be interesting candidates for the synthesis of metal nanoparticles. Indeed, through the ability to form inclusion complexes or supramolecular adducts with organic molecules or metal precursors, cyclodextrins can be successfully employed to stabilize size-controlled zerovalent metallic nanoparticles active for hydrogenation reactions carried out in aqueous or gas-phase media. In this summary of our works, we report that cyclodextrins could be used in various forms and environments: (i) in free form, (ii) in complexed form with appropriate guests molecules, (iii) in combination with polymer matrices, (iv) in thermosensitive hydrogels and (v) immobilized onto porous carbons supports. All these studies highlight the fact that cyclodextrins can be seen as multi-task agents for nanocatalysis

Synthèses et caractérisations de nanoparticules métalliques stabilisées en phase aqueuse par des polymères en présence de cyclodextrines (hydrogénation catalytique de composés issus de la biomasse)

Depuis les années 1990, les nanotechnologies connaissent un essor important. En catalyse notamment, les nanoparticules métalliques suscitent un intérêt croissant en raison de leurs propriétés à l interface entre catalyse homogène et hétérogène. Durant cette même période, un intérêt accru a été porté sur l utilisation de procédés catalytiques respectueux de l environnement en vue de l obtention de produits à hautes valeurs ajoutés. Afin de répondre à ces considérations environnementales, des nanoparticules métalliques (ruthénium et rhodium) synthétisées en phase aqueuse ont été utilisées, dans des conditions de température et de pression relativement douces, pour l hydrogénation de dérivés biosourcés hydrosolubles (furfural, 5-hydroxyméthylfurfural) ou non (3-(2-furyl)acroléine). Parmi les différents stabilisants existants, l utilisation de cyclodextrines associées à des polymères hydrosolubles a été particulièrement étudiée. Ces cyclodextrines ont pu être utilisées dans des mélanges polymère/cyclodextrine, ainsi que dans des polymères de cyclodextrines linéaires ou réticulés pour la stabilisation de nanoparticles. Durant cette thèse, les différents rôles de la cyclodextrine dans ces systèmes ont ainsi pu être mis en évidence : molécules fonctionnelles de polymères, agent de stabilisation, de dispersion ou de nucléation des nanoparticules mais également agent de transfert de phase lors de catalyse biphasique.Since the beginning of the 90s, nanotechnology has experienced a significant development. In catalysis, in particular, metallic nanoparticles have attracted a growing interest due to their properties at the interface between homogeneous and heterogeneous catalysis. At the same time, chemical reactions regarding the environment were the focus of a growing interest. To answer these environmental considerations, metallic nanoparticles (ruthenium and rhodium) synthesized in aqueous media were used, under mild conditions (temperature and pressure) for the hydrogenation of water-soluble biomass derivatives (furfural or 5-hydroxymethylfurfural) or insoluble (3-(2-furyl)acrolein). Among the different stabilizing agents, the use of cyclodextrins associated with water-soluble polymers was particularly studied. Cyclodextrins could be used in mixtures polymer/cyclodextrin, or in cyclodextrins polymers in two and three dimensions for the nanoparticles synthesis. Throughout this thesis, the various roles of cyclodextrine in these systems will be shown (crosslinking agent of polymers, stabilizing, dispersing or growth controlling agent of the nanoparticles and also phase transfer agent in biphasic catalysis).ARRAS-Bib.electronique (620419901) / SudocSudocFranceF

Continuous production of amines directly from alkenes via cyclodextrin-mediated hydroaminomethylation using only water as the solvent

Aqueous hydroaminomethylation (HAM) is an atom economical route for the efficient production of amines in one reaction step, starting from basic chemicals like alkenes. Herein we present the first successful establishment of a continuous process for HAM in an aqueous multiphase system. The green mass transfer agents randomly methylated-β-cyclodextrins (CD) enabled the catalytic system consisting of rhodium/sulfoXantphos to achieve high yields of up to 70% with selectivities of up to 80% in several continuous experiments with a total run time of more than 220 h. The key here is that water and products have large polarity differences, but the reaction still proceeds effectively due to the addition of cyclodextrin, which made the application of solvents obsolete. The main achievements in this way were the investigation of the influence of the randomly methylated-β-cyclodextrin concentration on the reaction rate and the selectivity in batch studies and finding promising operating points in the first continuous experiments. In a final experiment, the separation temperature was investigated. It was shown that the catalyst loss in the product phase is enormously small at 0.003% h−1 of the initial mass (0.24% in total), which is the lowest ever reported value for the HAM on this scale. Within a run time of 78 hours, 2.87 kg of tertiary amine were produced using only 0.2 g (>14[thin space (1/6-em)]000[thin space (1/6-em)]:[thin space (1/6-em)]1) of transition metal, while the loss of rhodium per kg of product produced was mostly around 0.15 mg kg−1, suggesting possible economical applicability

β-Cyclodextrins grafted with chiral amino acids: A promising supramolecular stabilizer of nanoparticles for asymmetric hydrogenation?

International audienceWater-soluble ruthenium nanoparticles stabilized by randomly methylated β-cyclodextrins (RaMeCDs) grafted with chiral amino-acid moieties like l-alanine (Ala) and l-leucine (Leu) were prepared in aqueous solution by two approaches: (i) a one-step hydrogen reduction of ruthenium trichloride as metal source in the presence of appropriate cyclodextrins (one-pot method) or (ii) a NaBH4 reduction of the metal salts, followed by the stabilization of ruthenium hydrosol by the addition of chirally modified RaMeCDs (cascade method). The influence of the ligand's nature and the synthesis methodologies on the size, dispersion and surface properties of the obtained ruthenium colloids were studied by TEM and NMR analyses. The spherical ruthenium suspensions contain very small particles (0.82-1.00 nm) with narrow size distributions. Their catalytic properties were evaluated in biphasic hydrogenation of various prochiral compounds (olefins, ketones and disubstituted arenes) showing promising results in terms of activity and selectivity. Nevertheless, no significant enantiomeric excesses were observed

Catalysis and cyclodextrins in liquid multiphase systems: State-of-theart, challenges and opportunities

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«Metallic nanoparticles and cyclodextrins in aqueous catalysis: Recent developments and future opportunities»

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Transition Metal Catalysis Involving Cyclodextrins Derivatives in Liquid Phase: New and Promising Developments

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Recent Advances in Hydroformylation, Hydrohydroxymethylation and hydroaminométhylation of Oleochemicals

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Transition metal catalysis involving cyclodextrin polymers in liquid phase: Recent results and future trends

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