Porous composite materials for CO2 conversion : synthesis, characterization, modelization

Dans le contexte de la transition énergétique le traitement du CO2, vecteur du réchauffement climatique, est un enjeu majeur. Une solution possible est sa conversion en produits à haute valeur ajoutée tels que le monoxyde de carbone, le méthane ou encore le formiate, par réduction photo- ou électro-catalytique. L’emploi de catalyseurs est nécessaire pour effectuer ces réactions. Dans cette thèse sont présentés quatre types de photocatalyseurs hétérogènes utilisés pour la réduction du CO2, à base de polyoxométallates (POMs), de metal-organic frameworks (MOFs) ou de polymères organiques poreux (POPs). Ces travaux montrent d’une part, que l’immobilisation de POMs dans des MOFs (POM@MOF) a un effet important sur la structure et les propriétés catalytiques des photosystèmes et d’autre part, que l’hétérogénéisation du photosensibilisateur dans des matériaux poreux augmente grandement leur stabilité en régime photocatalytique. L’utilisation d’outils variés issus de plusieurs disciplines – chimie théorique, chimie analytique – permet une description détaillée à l’échelle atomique des relations structures-propriétés des photosystèmes étudiés. En particulier, il est montré que cette compréhension ne serait pas possible sans cette pluridisciplinarité.In the context of the energetic transition, CO2 treatment – vector of global warming – is a major goal. One possible route is its conversion in high added-value products such as carbon monoxide, methane or formate using photo- or electro-catalytic reduction. The use of catalyst is necessary for these reactions. In this thesis four types of photocatalysts are presented for CO2 reduction based on polyoxometalates (POMs), metal-organic frameworks (MOFs) or porous organic polymers (POPs). This work shows on the one hand that the immobilisation of POMs into MOFs (POM@MOF) has a significant effect on the structural and catalytic properties of the photosystems. On the other hand, it shows that heterogenisation of the photosensitizer in the matrix of the materials highly enhances their stability in catalytic conditions. The use of various tools from many areas in chemistry – theoretical, analytical – allows a detailed description at the atomic scale of the structure-property relationships of the studied photosystems. In particular, it is shown that such interpretation would not be possible without this pluridisciplinarity

Matériaux composites poreux pour la conversion du CO2 : synthèse, caractérisation et modélisation

In the context of the energetic transition, CO2 treatment – vector of global warming – is a major goal. One possible route is its conversion in high added-value products such as carbon monoxide, methane or formate using photo- or electro-catalytic reduction. The use of catalyst is necessary for these reactions. In this thesis four types of photocatalysts are presented for CO2 reduction based on polyoxometalates (POMs), metal-organic frameworks (MOFs) or porous organic polymers (POPs). This work shows on the one hand that the immobilisation of POMs into MOFs (POM@MOF) has a significant effect on the structural and catalytic properties of the photosystems. On the other hand, it shows that heterogenisation of the photosensitizer in the matrix of the materials highly enhances their stability in catalytic conditions. The use of various tools from many areas in chemistry – theoretical, analytical – allows a detailed description at the atomic scale of the structure-property relationships of the studied photosystems. In particular, it is shown that such interpretation would not be possible without this pluridisciplinarity.Dans le contexte de la transition énergétique le traitement du CO2, vecteur du réchauffement climatique, est un enjeu majeur. Une solution possible est sa conversion en produits à haute valeur ajoutée tels que le monoxyde de carbone, le méthane ou encore le formiate, par réduction photo- ou électro-catalytique. L’emploi de catalyseurs est nécessaire pour effectuer ces réactions. Dans cette thèse sont présentés quatre types de photocatalyseurs hétérogènes utilisés pour la réduction du CO2, à base de polyoxométallates (POMs), de metal-organic frameworks (MOFs) ou de polymères organiques poreux (POPs). Ces travaux montrent d’une part, que l’immobilisation de POMs dans des MOFs (POM@MOF) a un effet important sur la structure et les propriétés catalytiques des photosystèmes et d’autre part, que l’hétérogénéisation du photosensibilisateur dans des matériaux poreux augmente grandement leur stabilité en régime photocatalytique. L’utilisation d’outils variés issus de plusieurs disciplines – chimie théorique, chimie analytique – permet une description détaillée à l’échelle atomique des relations structures-propriétés des photosystèmes étudiés. En particulier, il est montré que cette compréhension ne serait pas possible sans cette pluridisciplinarité

Matériaux composites poreux pour la conversion du CO2 : synthèse, caractérisation et modélisation

In the context of the energetic transition, CO2 treatment – vector of global warming – is a major goal. One possible route is its conversion in high added-value products such as carbon monoxide, methane or formate using photo- or electro-catalytic reduction. The use of catalyst is necessary for these reactions. In this thesis four types of photocatalysts are presented for CO2 reduction based on polyoxometalates (POMs), metal-organic frameworks (MOFs) or porous organic polymers (POPs). This work shows on the one hand that the immobilisation of POMs into MOFs (POM@MOF) has a significant effect on the structural and catalytic properties of the photosystems. On the other hand, it shows that heterogenisation of the photosensitizer in the matrix of the materials highly enhances their stability in catalytic conditions. The use of various tools from many areas in chemistry – theoretical, analytical – allows a detailed description at the atomic scale of the structure-property relationships of the studied photosystems. In particular, it is shown that such interpretation would not be possible without this pluridisciplinarity.Dans le contexte de la transition énergétique le traitement du CO2, vecteur du réchauffement climatique, est un enjeu majeur. Une solution possible est sa conversion en produits à haute valeur ajoutée tels que le monoxyde de carbone, le méthane ou encore le formiate, par réduction photo- ou électro-catalytique. L’emploi de catalyseurs est nécessaire pour effectuer ces réactions. Dans cette thèse sont présentés quatre types de photocatalyseurs hétérogènes utilisés pour la réduction du CO2, à base de polyoxométallates (POMs), de metal-organic frameworks (MOFs) ou de polymères organiques poreux (POPs). Ces travaux montrent d’une part, que l’immobilisation de POMs dans des MOFs (POM@MOF) a un effet important sur la structure et les propriétés catalytiques des photosystèmes et d’autre part, que l’hétérogénéisation du photosensibilisateur dans des matériaux poreux augmente grandement leur stabilité en régime photocatalytique. L’utilisation d’outils variés issus de plusieurs disciplines – chimie théorique, chimie analytique – permet une description détaillée à l’échelle atomique des relations structures-propriétés des photosystèmes étudiés. En particulier, il est montré que cette compréhension ne serait pas possible sans cette pluridisciplinarité

Structure-directing role of immobilized polyoxometalates in the synthesis of porphyrinic Zr-based metal–organic frameworks

International audienceWe evidence the structure-directing role of the PW12O403-polyoxometalate in the synthesis of porphyrinicMOFswhereby it promotes the formation of the kinetic topology. Its immobilization into the MOF is successfully achieved at high temperature yielding the kinetic MOF-525/PCN-224 phases, while prohibiting the formation of the thermodynamic MOF-545 product. A combined experimental and theoretical approach uses differential PDF and DFT calculations along with solid-state NMRto show the structural integrity of the hosted POM andits location in the vicinity of the Zr-based nodes

Heterogenization of a Molecular Ni Catalyst within a Porous Macroligand for the Direct C-H Arylation of Heteroarenes

International audienceDirect C–H functionalization catalyzed by a robust and recyclable heterogeneous catalyst is highly desirable for sustainable fine chemical synthesis. Bipyridine units covalently incorporated into the backbone of a porous organic polymer were used as a porous macroligand for the heterogenization of a molecular nickel catalyst. A controlled nickel loading within the porous macroligand is achieved, and the nickel coordination to the bipyridine (bpy) sites is assessed at the molecular level using IR and solid-state NMR spectroscopy. The heterogenized Ni-bpy catalyst was successfully applied to the direct and fully selective C2 arylation of benzothiophenes, thiophene, and selenophene, as well as for the arylation of free NH-indole. Recyclability of the catalyst was achieved by employing hydride activators to reach a cumulative turnover number of more than 300 after seven cycles of catalysis, which corresponds to a total productivity of 12 g of 2-phenylbenzothiophene, chosen as model target biaryl, per gram of catalyst

Co-immobilization of a Rh Catalyst and a Keggin Polyoxometalate in the UiO-67 Zr-Based Metal–Organic Framework: In Depth Structural Characterization and Photocatalytic Properties for CO2 Reduction

International audienceThe Keggin-type polyoxometalate (POM) PW12O403– and the catalytic complex Cp*Rh(bpydc)Cl2 (bpydc = 2,2′-bipyridine-5,5′-dicarboxylic acid) were coimmobilized in the Zr(IV) based metal organic framework UiO-67. The POM is encapsulated within the cavities of the MOF by in situ synthesis, and then, the Rh catalytic complex is introduced by postsynthetic linker exchange. Infrared and Raman spectroscopies, 31P and 13C MAS NMR, N2 adsorption isotherms, and X-ray diffraction indicate the structural integrity of all components (POM, Rh-complex and MOF) within the composite of interest (PW12,Cp*Rh)@UiO-67. DFT calculations identified two possible locations of the POM in the octahedral cavities of the MOF: one at the center of a UiO-67 pore with the Cp*Rh complex pointing toward an empty pore and one off-centered with the Cp*Rh pointing toward the POM. 31P–1H heteronuclear (HETCOR) experiments ascertained the two environments of the POM, equally distributed, with the POM in interaction either with the Cp* fragment or with the organic linker. In addition, Pair Distribution Function (PDF) data were collected on the POM@MOF composite and provided key evidence of the structural integrity of the POM once immobilized into the MOF. The photocatalytic activity of the (PW12,Cp*Rh)@UiO-67 composite for CO2 reduction into formate and hydrogen were evaluated. The formate production was doubled when compared with that observed with the POM-free Cp*Rh@UiO-67 catalyst and reached TONs as high as 175 when prepared as thin films, showing the beneficial influence of the POM. Finally, the stability of the composite was assessed by means of recyclability tests. The combination of XRD, IR, ICP, and PDF experiments was essential in confirming the integrity of the POM, the catalyst, and the MOF after catalysis

Unveiling the mechanism of the photocatalytic reduction of CO 2 to formate promoted by porphyrinic Zr-based metal–organic frameworks

International audienceA complete picture of the reaction mechanism driving the photocatalytic reduction of CO 2 into formate promoted by the Zr-based porphyrinic MOF-545 in CH 3 CN/TEOA solutions is provided for the first time by combining experimental and computational approaches

Molecular Porous Photosystems Tailored for Long-Term Photocatalytic CO2 Reduction

RMN+ECI2D:ING+FWI:AGH:YMO:CLO:DFA:JECInternational audienceHerein, we report the molecular-level structuration of two full photosystems into conjugated porous organic polymers. The strategy of heterogenization gives rise to photosystems which are still fully active after 4 days of continuous illumination. Those materials catalyse the carbon dioxide photoreduction driven by visible light to produce up to three grams of formate per gram of catalyst. The covalent tethering of the two active sites into a singleframework is shown to play a key role in the visible light activation of the catalyst. The unprecedented long-term efficiency arises from an optimal photoinduced electron transfer from the light harvesting moiety to the catalytic site as anticipated by quantum mechanical calculations and evidenced by in-situ ultrafast time-resolved spectroscopy