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Le développement de technologies plus propres et économes en énergie amène aujourd’hui l’industrie du raffinage à modifier ses stratégies de préparation de catalyseurs et à se tourner vers l'utilisation plus massive de catalyseurs hétérogènes plus actifs, sélectifs, stables et régénérables.Récemment une méthode originale a été développée par Dufaud et al. (J. Mater. Chem., 2009, 19, 1142-1150) pour encapsuler des polyoxométallates (POMs) dans les murs des silices mésoporeuses. Le projet de thèse a visé l’élaboration de nouveaux catalyseurs basés sur cette nouvelle méthodologie qui devrait conduire à des systèmes à haute teneur en métal actif Mo/W bien dispersé, avec une meilleure proximité spatiale entre le Mo/W et son promoteur. Afin de mettre en évidence cette proximité, différentes voies ont été envisagées :i) synthèse en deux étapes comportant l'encapsulation des POMs dans les murs de SBA-15, suivie d’une imprégnation à sec des promoteurs (Ni(NO3)2 ou Co(NO3)2)ii) synthèse en une seule étape comportant l'imprégnation à sec de POMs substitués Co3PCoMo11O40H, Ni3PNiMo11O40H, Co3/2PMo12O40 ou Ni3/2PMo12O40 iii) préparation traditionnelle par co-Imprégnation à sec d’une silice SBA-15 par une solution de POMs et Ni(NO3)2 ou Co(NO3)2, afin de mettre en évidence non seulement l'intérêt de la nouvelle méthode de préparation mais aussi le gain lié à l'utilisation de supports de type SBA-15 (par rapport aux supports aluminiques conventionnels) ayant des caractéristiques texturales aussi remarquables. L’effet du traitement de sulfuration sur ces solides a été étudié et l’évaluation des propriétés catalytiques de ces matériaux a été réalisée sur des molécules modèles en hydrogénation du toluène, hydrodésulfuration du thiophène et du 4,6-DMDBT. A partir des résultats obtenus, une des stratégies de synthèse a été optimisée, en vue de l'élaboration de matériaux encore plus actifs. / Economic growth in the developing countries over the past decade has increased the global demand for crude oil. It is projected that the global crude slate will become sourer, with a sulfur content above 1.3 wt%. An overall aim of policymakers is thus to ensure that transportation fuels do not surpass a sulfur content of 10 ppm. Several solutions are possible to achieve the nowadays goals, that affect either the process or the catalyst. The latter solution, which does not involve significant additional costs for refiners, is therefore the most studied. One way to improve the nowadays catalysts would be to increase the content of active metal (eg cobalt and molybdenum in the case of CoMo systems). Nevertheless, at higher metal loadings, the formation of refractory species such as CoMoO4 or Co3O4 by sintering during calcination and/or sulfidation steps has been reported for alumina-Supported catalysts. This PhD project is based on the development of new hydrotreating catalysts, through a 2-Step one-Pot method : synthesis of polyoxometalates-Containing mesoporous SBA-15 materials, followed by incipient wetness impregnation of active phase promoter. The encapsulation of these species within the silica matrix would prevent the agglomeration of large particles during sulfidation reactions and could thus lead to systems with high content of active metal well dispersed over the support. One aim of this study was to evaluate the potential of these catalysts in the hydrotreating of several feedstocks, such as diesel oil, gasoline or vegetal oil. A second objective was the understanding of the nature of the different interactions between the active phase precursors and the support, according to each preparation technique.The non-Promoted hybrid catalyst showed a better dispersion of the metallic phase in the oxide state, compared to the catalysts prepared by incipient wetness impregnation, which can be correlated with stronger interactions between encapsulated POM and silica functionalities, such as siloxanes and silanols, as evidenced by Raman spectroscopy. However, the wide-Angle XRD showed the presence of MoO3 crystallites. HRTEM analyzes of the sulfided catalysts showed different species on this catalyst: small MoS2 slabs and metal particles (∼ 1 nm) mainly in the walls but also on the surface of pores; curved MoS2 slabs at mesopores surface leaving the entrance of the pore free; MoS2 hanks blocking the pores.This catalyst showed a relatively low sulfidation rate (determined by XPS), which could be associated with the presence of refractory species already present before activation. Thus, the toluene conversion represented per MoS2 clearly showed the interest of the catalyst prepared by this innovative method, presenting an intrinsic activity two-Fold higher than that of the catalyst prepared by dry impregnation.The subsequent impregnation of the active phase promoter of the hybrid catalyst (Pr(NO3)2, Pr = Ni or Co; 4 <pH <6), resulted in a very heterogeneous distribution of species, which could be attributed to a POM destruction by the impregnation solution, that afterward led to the sintering of large clusters. However, the hybrid catalysts promoted showed improved catalytic performances when compared to the traditional alumina-Based catalysts, when nickel is used as a promoter. However, the sulfidation and promotion rates of these catalysts must be improved: the catalyst with the highest Ni content showed (i) a high Ni/Mo atomic ratio of 0.4, which would lead to a loss of active sites by excessive decoration, and (ii) the formation of species such as NixOwSy or NixSy, which could lead to the loss of active sites, dispersion and access to the active phase.Perspectives towards an enhanced HDT catalyst based on the findings of this project are:Milder synthesis calcination conditionsSulfidationPost-Synthetic treatment in order to introduce Ni and Mo in proximal vicinityRegeneration of HDT hybrid catalysts

Ce mémoire porte sur la synthèse de matériaux composites nanostructurés à base de polyoxométallates pour la conversion de l’énergie et des applications à des problèmes environnementaux. Pour atteindre ces objectifs, de nombreux composés nouveaux de cette famille d’oxydes moléculaires ont été synthétisés puis ont été associés à différentes matrices éco-compatibles dans le respect des principaux critères de la Chimie Verte. Les principales techniques d’étude sont l’électrochimie, la photochimie et la spectroscopie UV-visible. Dans le domaine de l’énergie, les catalyseurs obtenus se sont révélés très efficaces dans des réactions très importantes mais difficiles à réaliser, comme la production de l’hydrogène, la réduction de l’oxygène et l’oxydation de l’eau. De même, parmi les applications aux problèmes de dépollution, ces nanomatériaux ont montré une forte activité électrocatalytique et photocatalytique pour la réduction des oxydes d’azote, des bromates et la photodégradation d’un colorant textile toxique, l’Acide Orange 7. Les performances de ces nouveaux catalyseurs sont comparables à celles des meilleurs systèmes connus. / This thesis focuses on the synthesis of nanostructured composite materials based on polyoxometalates for energy conversion and applications to environmental problems. To achieve these goals, many new compounds of this family of molecular oxides were synthesized and were associated with different nature friendly matrices, in agreement with the main criteria of Green Chemistry. In the field of energy, the new catalysts have proved very effective in important but difficult to achieve reactions, such as producing hydrogen, oxygen reduction or water oxidation. Similarly, among applications to pollution problems, these nanomaterials have shown a strong electrocatalytic and photocatalytic activity for the reduction of nitrogen oxides, bromate and for the photodegradation of a toxic textile dye, Acid Orange 7. The performances of these new catalysts are comparable to those of the best known systems.

Ø / The dissertation is presented on 252 content pages which has been framed in five chapters and two annexures while the title page opens into a list of abbreviations followed by a foreword on the work. The core theme of the research work is to validate the extended photocatalytic properties of porphyrin-POM materials in evolving from UV to visible light range of solar spectrum. Which describing additional modes for synthesis of hybrid materials (i) electrostatic multilayer’s comprising of Dawson , sandwich Dawson type and preyssler,s POM in combination with free base tetracationic porphyrin [H₂TPhN(Me)₃P⁴⁺] (ii) an easy method of synthesis of two dimers with a pyridinium spacer (abbreviated 4-H₂–Zn and 3-H₂–Zn) (iii) Langmuir Schafer approach for hybrid monolayer. The prepared photoactive thin layers have been characterized by UV-visible spectroscopy and fluorescence spectroscopy for optical properties. Cyclic voltammetry for electrochemistry and ionic permeability studies. Atomic force microscopy (AFM) for surface morphology and its role in physical mechanism of reduction process and shape of nanostructures obtained. Transmission electron microscopy (TEM) has been used to interpret size and shape of dendritic silver nanoparticles obtained as photoreduction product. Although ,the ultimate goal is the photoreduction of heavy metals (Cr(VI), Hg(II), Cd(II), Pb(II) ), reduction of a simpler system like Ag⁺ ion has been chosen as a model system due to single electron simpler oxidation reduction process. A novel application of photocurrent generation from these hybrid films has been demonstrated in the fifth chapter of the manuscript as an initial studies which has enhanced the significance of all previously fabricated systems upto by many folds .The foresaid development of photovoltaic application has paved the way for future studies to enhance the photocurrent yield further by tuning the electron donor-acceptor system. Both components porphyrin and POM can be tuned with different axial substituent’s and stereo chemical properties to achieve maximum yield of solar energy as well as diversified metal nanostructure for nanoelectronics, e.g. silver dendrites for sensor applications. At the end of the manuscript, three appendices describe successively the experimental techniques used to carry out this work, the Job method used to determine the stoichiometry and formation constants of complex electrostatic and coordination, and then finally the origin or Protocols for the synthesis of various compounds used.

Filmes híbridos fotoativos de Ormosil (silicatos organicamente modificados) contendo o polioxometalato de Keggin ácido fosfotungstico (H3PW12O40) e cátions Ag+ foram preparados por meio da rota sol-gel e deposição de filme por dip-coating. A caracterização por FTIR, Raman, XRF e DRX evidenciou a formação da matriz de organossilicato e o aprisionamento dos poliânions PW12O403- e cátions Ag+. O comportamento fotocrômico dos filmes de Ormosil-fosfotungstato baseiam-se na redução fotoinduzida do fosfotungstato por exposição à radiação UV, o que leva à formação de compostos coloridos de valência mista conhecidos como heteropolyblues. No entanto, a presença de cátions Ag+ altera completamente o comportamento fotocrômico destes filmes híbridos. Os poliânions de fosfotungstato fotorreduzidos são agentes redutores eficientes na redução dos cátions Ag+, resultando na formação in situ de nanopartículas de prata metálica na matriz híbrida como evidenciado pela intensa banda plasmônica centrada em 390 nm no espectro eletrônico da amostra. A caracterização por Uv-vis e Espectroscopia de Absorção de Raios X próxima a Borda de Absorção (XANES) mostrou que a foto-redução pode ser revertida por tratamento térmico o que caracteriza um comportamento fotocrômico reversível. O comportamento cinético da amostra foi analisado propondo mecanismos para as reações de redução e oxidação da prata, responsáveis pela alteração de coloração do material. O aprisionamento de compostos fotoativos em matrizes híbridas orgânico-inorgânico via sol-gel é uma estratégia interessante para a preparação de materiais fotocrômicos com potenciais aplicações tecnológicas. A reversibilidade fotocrômica destes materiais os torna bons candidatos para aplicação em sistemas de memória óptica, filtros óticos de passa-banda estreita, dispositivos de ótica não linear, sensores de radiação UV e revestimentos bactericidas. / Sol gel entrapment of photoactive compounds in organic-inorganic hybrid matrices is an interesting strategy for the preparation of photochromic materials with potential technological applications. In this study, we report the preparation of photoactive Ormosil (organically modified silicates) hybrid films containing the Keggin polyoxometalate phosphotungstate (H3PW12O40) and Ag+ cations by sol-gel synthesis and dip coating deposition. The materials have been characterized by infrared absorption spectroscopy (FTIR), Raman spectroscopy and X-ray Fluorescence (XRF), thus evidencing the formation of hybrid organosilicate matrix and the entrapment of the PW12O40-3 polyanions and Ag+ cations. The photochromic behavior of the Ormosil-phosphotungstate films is based on photoinduced reduction of phosphotungstate upon exposure to UV radiation, which leads to the formation of colored mixed valence compounds known as heteropolyblues. However, the presence of Ag+ cations completely changes the photochromic behavior of these hybrid films. The photoreduced phosphotungstate polyanions rapidly promote the reduction of Ag+ cations, resulting in the in situ formation of silver metal nanoparticles (Ag0) inside the hybrid matrix as evidenced by the intense plasmonic band centered at 390nm as shown by electronic, UV-vis, spectroscopy and its yellowish color. The Uv-vis and X-ray Near Edge Absorption Spectroscopy (XANES) characterization shown that this process is reversible and the yellowish color characteristic of the metallic silver nanoparticles disappears once the hybrid films are heated at 353 K. Thus, the coloration is achieved upon UV exposure and discoloration occurs upon simple heating. Therefore, the described photoactive properties, the prepared hybrid films have potential application in optical memory systems, single bandpass optical filters, non-linear optical devices, UV radiation sensors and bactericidal coatings.

Les polyoxométallates (POMs) de type Keggin [XM12O40]n- (avec X=P… et M= W, Mo …) sont des oxydes moléculaires de métaux de transition à haut degré d’oxydation qui présentent des réductions successives et réversibles dans une gamme étroite de potentiel. Leur incorporation dans des dispositifs de mémoire moléculaire semble alors prometteuse. Nous avons développé leur intégration comme briques élémentaires via une approche “bottom-up” qui surmonte les limites de l’approche “top-down” plus commune. Cela nécessite un contrôle fin de leur greffage et de leur densité surfacique pour l’obtention de dispositifs performants. Nous avons donc développé le greffage covalent de POMs sur des surfaces à base de silicium et d’or. Des hybrides de POMs à terminaison diazonium BA3[PM11O39{SnC6H4C≡CC6H4N2}] (avec M=W or Mo) ont formé des monocouches complètes greffées sur des surfaces de silicium hydrogénées qui mettent en évidence l’influence du métal constitutif du fragment polyoxométallate sur les propriétés de transport de charges de la jonction. Le greffage d’hybrides de POM à terminaison acide carboxylique sur des substrats d’oxyde de silicium a aussi été développée. Un hybride de POM à terminaison aniline TBA4[PW11O39{SnC6H4C≡CC6H4NH2}] a été greffé en deux étapes via un couplage peptidique sur une monocouche à terminaison acide carboxylique sur surface d’or. Des monocouches compactes ont été obtenues mais pas de façon totalement reproductible et les premiers essais de dilution sont encourageants. Une nouvelle famille d’hybrides de POMs mixtes a été synthétisée : TBA4[PMoxW11-xO39{SnR}]. Cela permettra de combiner les propriétés redox du molybdène et la robustesse due au tungstène. / Keggin type polyoxometalates (POMs) [XM12O40]n- (with X=P… and M= W, Mo…) are molecular oxides of early transition metals with a high oxidation state. They present electrochemical successive reversible reduction waves in a narrow range of potential. This makes them good candidates to be incorporated into molecular memory devices. We chose a “bottom-up” approach where the POMs are the building blocks to overcome the limitation of the “top-down” process commonly used. A fine control of the POM grafting and of the surface density is essential to get better erase/writing time of the device. So, we developed POM hybrids for grafting them covalently onto silicon based and gold substrates. Diazonium-terminated POM hybrids (with M=W or Mo) lead to compact homogeneous monolayers onto hydrogenated silicon surfaces. Electrical measurements of the two analogous modified surfaces show different behaviour highlighting the role of the constituting POM metal into the charge transport. Carboxylic-terminated POM hybrids have also been grafted in a one-step process onto silicon oxide surface resulting in a smooth and dense monolayer. Then, an aniline-terminated POM hybrid has been grafted onto a carboxylic-terminated SAM of thiols onto gold thanks to a peptide coupling. Compact monolayers have been obtained without complete reproducibility and the first attempts of dilution are encouraging. A new family of POM hybrids have been synthesized: mixed-metal POM hybrids TBA4[PMoxW11-xO39{SnR}]. This will permit to combine the electrochemical properties of molybdenum and the robustness of tungsten.

Nowadays, the modern chemical industry has to deal with increasing environmental concerns, including the disposal of waste and its economic impact, or the diminution of important worldwide resources such as transition metals. In this Ph.D. thesis, we aimed to bring improvement in this area by the development of green processes, based on the use of recyclable heterogeneous catalysts. By combining the catalytic properties of several metal cations with the properties of solid catalysts such as polyoxometalates or zeolites, we were able to set up new tools for organic synthesis. Silver-doped polyoxometalates proved to be very efficient catalysts in the rearrangement of alkynyloxiranes to furans. Acetals and spiroketals were synthetized by dihydroalkoxylation of alkynediols under catalysis with silver-zeolites. As a perspective, we highlighted the potential applications of such green procedures in the total synthesis of more complex molecules. The first results suggested that these environmental friendly processes should gain increasing interest in the future.

Filmes híbridos fotoativos de Ormosil (silicatos organicamente modificados) contendo o polioxometalato de Keggin ácido fosfotungstico (H3PW12O40) e cátions Ag+ foram preparados por meio da rota sol-gel e deposição de filme por dip-coating. A caracterização por FTIR, Raman, XRF e DRX evidenciou a formação da matriz de organossilicato e o aprisionamento dos poliânions PW12O403- e cátions Ag+. O comportamento fotocrômico dos filmes de Ormosil-fosfotungstato baseiam-se na redução fotoinduzida do fosfotungstato por exposição à radiação UV, o que leva à formação de compostos coloridos de valência mista conhecidos como heteropolyblues. No entanto, a presença de cátions Ag+ altera completamente o comportamento fotocrômico destes filmes híbridos. Os poliânions de fosfotungstato fotorreduzidos são agentes redutores eficientes na redução dos cátions Ag+, resultando na formação in situ de nanopartículas de prata metálica na matriz híbrida como evidenciado pela intensa banda plasmônica centrada em 390 nm no espectro eletrônico da amostra. A caracterização por Uv-vis e Espectroscopia de Absorção de Raios X próxima a Borda de Absorção (XANES) mostrou que a foto-redução pode ser revertida por tratamento térmico o que caracteriza um comportamento fotocrômico reversível. O comportamento cinético da amostra foi analisado propondo mecanismos para as reações de redução e oxidação da prata, responsáveis pela alteração de coloração do material. O aprisionamento de compostos fotoativos em matrizes híbridas orgânico-inorgânico via sol-gel é uma estratégia interessante para a preparação de materiais fotocrômicos com potenciais aplicações tecnológicas. A reversibilidade fotocrômica destes materiais os torna bons candidatos para aplicação em sistemas de memória óptica, filtros óticos de passa-banda estreita, dispositivos de ótica não linear, sensores de radiação UV e revestimentos bactericidas. / Sol gel entrapment of photoactive compounds in organic-inorganic hybrid matrices is an interesting strategy for the preparation of photochromic materials with potential technological applications. In this study, we report the preparation of photoactive Ormosil (organically modified silicates) hybrid films containing the Keggin polyoxometalate phosphotungstate (H3PW12O40) and Ag+ cations by sol-gel synthesis and dip coating deposition. The materials have been characterized by infrared absorption spectroscopy (FTIR), Raman spectroscopy and X-ray Fluorescence (XRF), thus evidencing the formation of hybrid organosilicate matrix and the entrapment of the PW12O40-3 polyanions and Ag+ cations. The photochromic behavior of the Ormosil-phosphotungstate films is based on photoinduced reduction of phosphotungstate upon exposure to UV radiation, which leads to the formation of colored mixed valence compounds known as heteropolyblues. However, the presence of Ag+ cations completely changes the photochromic behavior of these hybrid films. The photoreduced phosphotungstate polyanions rapidly promote the reduction of Ag+ cations, resulting in the in situ formation of silver metal nanoparticles (Ag0) inside the hybrid matrix as evidenced by the intense plasmonic band centered at 390nm as shown by electronic, UV-vis, spectroscopy and its yellowish color. The Uv-vis and X-ray Near Edge Absorption Spectroscopy (XANES) characterization shown that this process is reversible and the yellowish color characteristic of the metallic silver nanoparticles disappears once the hybrid films are heated at 353 K. Thus, the coloration is achieved upon UV exposure and discoloration occurs upon simple heating. Therefore, the described photoactive properties, the prepared hybrid films have potential application in optical memory systems, single bandpass optical filters, non-linear optical devices, UV radiation sensors and bactericidal coatings.