Search

This thesis aimed at the construction of porous coordination polymer (PCP, or MOFs Metal-Organic Frameworks for) within macroporous alumina membranes (Øpores ˜ 200 nm), whose role is twofold. Obtained as crystals, MOFs are fragile. The membrane firstly provides a protective shell for the coordination polymer embedded in the composite material. Moreover, the membrane acts as a matrix, enabling the elaboration of one-dimensional nanostructures (1D), obtained after selective elimination of the matrix. The functionalization of the membrane, and the experimental parameters (reagents concentration, number of cycles, intermediate washing-step...) have been widely studied. They allowed accessing various PCP/membrane composites. Composites involving HKUST-1, ZIF-8 and Fe(pz)[Ni(CN)4] spin transition MOFs have been prepared. For the coordination polymer ZIF-8, 1D nanofibers have been successfully isolated after dissolution of the membrane. These composites and the resulting nano-objects have been extensively characterized in terms of morphology (SEM, TEM, AFM), chemical composition (Raman, XRD, IR), and properties (magnetic or gas adsorption / desorption).; Cette thèse concerne la mise en forme et la structuration de polymères de coordination poreux (PCP, ou MOFs pour Metal-Organic Frameworks) au sein de membranes d'alumine macroporeuses (Øpores ˜ 200 nm), dont le rôle est double. Obtenus sous forme de cristaux, les MOFs sont fragiles. La membrane constitue d'une part une coque protectrice pour le polymère de coordination impliqué dans le matériau composite. D'autre part, elle fait office de matrice, permettant la fabrication de nanostructures unidimensionnelles (1D), obtenues après élimination sélective de la dite matrice. La fonctionnalisation préalable de la membrane, ainsi que les paramètres opératoires (concentration en réactifs, nombre de cycle de filtration, étape de lavage intermédiaire...) ont été largement étudiés, ce qui a permis d'élaborer avec succès plusieurs composites PCP/membrane. Ainsi, des composites incluant des PCP tels que HKUST-1, ZIF-8, et un matériau à transition de spin Fe(pz)[Ni(CN)4] ont été préparés. Pour le polymère de coordination ZIF-8, des nanofibres 1D ont été isolées avec succès après dissolution de la membrane. Tous les composites et les nano-objets résultants ont été amplement caractérisés en termes de morphologie (MEB, MET, AFM), de composition chimique (Raman, DRX, IR), et de propriétés (magnétiques ou d'adsorption/désorption de gaz).

National audience; PCPs (Porous Coordination Polymers) or MOFs (Metal Organic Frameworks) are crystalline materialswhose structures consist of metal-based nodes bridged by organic linking groups. They are a well known class of porous materials which can have applications in gas storage (H2, CH4, CO2…), heterogeneous catalysis and chemical sensors.1 Up to now the main strategy to increase the absorption properties has been to introduce coordinatively unsaturated metal centres. In contrast, the incorporation of cationic organic ligands is much rarer despite a certain potential as shown by some reports.2 Our original approach consists of mixing electro-active viologen derivatives to a useful coordination function like carboxylate, which is widely used in such materials,3 to synthesize new PCPs for gas storage and molecular recognition. Those ligands are based on N-substituted-4,4’-bipyridinium monocation and N,N’-disubstituted-4,4’-bipyridinium dication carrying one or several carboxylate groups. Our synthetic strategy and new results will be described in this poster, taking the [Cd4Cl6L3](CdCl4) compound as example, with L = 4,4’-bipy-(C6H4COO)2. In addition to provide a highly stable structure upon temperature and moisture, this PCP exhibits accessible channels with a large zwitterionic surface area which allow reversible sorption properties of gas and small molecules. The obvious color shift in presence of ammonia vapors offers a high potential for chemical sensors and optical applications.

National audience; Porous coordination polymers (PCP) or metal−organic frameworks (MOF) have focused attention going from synthetic strategy to applications in heterogeneous catalysis, molecular recognition and gas storage. Up to now the main strategy to increase the sorption abilities has been to introduce coordinatively unsaturated metal centres. Only few examples have been reported based on the assembly of cationic bridging ligands. Our original approach consists in combining the coordination versatility of carboxylate functions, commonly used in this field, to electro-active viologen derivatives in order to synthesize new porous coordination polymers for gas storage and redox mediators with optical and magnetic properties. The designed ligands are based on N-substituted-4,4’-bipyridinium monocation and N,N’-disubstituted-4,4’-bipyridinium dication bearing one or several carboxylate groups. In addition to act as charge-separated organic linkers, these pyridinium-carboxylate ligands will i) afford a cationic surface to enhance the interactions with guests and ii) exhibit reversible redox states involving monocationic radicals with good stability and large absorptions coefficients in the visible range. Some of our new results will be presented here and a particular attention will be dedicated to compounds that also exhibit thermo-, solvato- and photo-chromic behavior.&nbsp

International audience; Porous coordination polymers or metal−organic frameworks have focused attention going from synthetic strategy to applications in heterogeneous catalysis, molecular recognition and gas storage. Our approach consists in combining the coordination versatility of carboxylate functions to electro-active viologen derivatives (N,N’-disubstituted 4,4’-bipyridinium salts) with general formula (OOCC6H4)2(4,4’-bipy) in order to synthesized new porous coordination polymers for gas storage and redox mediators with optical and magnetic properties. In addition to act as charge-separated organic linkers, these pyridinium-carboxylate ligands will i) afford a cationic surface to enhance the interactions with guests and ii) exhibit reversible redox states involving monocationic radicals with good stability and large absorptions coefficients in the visible range.