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Theses

Hybrids of Polyoxometalates supported on mesoporous silica and magnetic core-shell nanoparticles for anchored homogeneous catalysis

Abstract : New materials based on silica oxides (mesoporous silica SBA-15, magnetic core-shell nanoparticles) combined with nucleophilic hybrids of (vacant) polyoxometalates were elaborated for applications in the field of anchored homogeneous catalysis for mild oxidations reactions. The main parameter taken into account was the formation of a covalent bond between the support and the POMs. Two different pathways were followed depending upon the support used for the covalently grafting of POMs. Firstly, Keggin type POMs bearing carboxylic acid functions were grafted onto amino-functionalized SBA-15. Using the same support, other covalent immobilization methods were tried out, such as the use of a cross-linker. Secondly, hybrid nanocatalysts based on magnetic core-shell nanoparticles grafted with POMs were synthesized. All materials were characterized by a wide variety of physicochemical techniques. By HR TEM, the POMs were localized inside the pores of SBA-15 and onto the surface of magnetic core shell NPs, showing an excellent nanostructuration on the surface of both materials. Furthermore, the catalytic activity of the synthesized anchored homogeneous catalysts has been evaluated through the epoxidation of cyclooctene and cyclohenexe with H2O2 in acetonitrile, resulting in fairly good conversions in some cases, compared to the homogeneous systems used in this study. Finally, particular attention was paid to the excellent catalytic behavior of POMs bearing carboxylic acid functions compared to other POMs of the same family. Thus, DFT calculations were performed in order to identify the cause of this enhanced reactivity.
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https://tel.archives-ouvertes.fr/tel-01717294
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Submitted on : Monday, February 26, 2018 - 10:56:07 AM
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  • HAL Id : tel-01717294, version 1

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Ourania Makrygenni. Hybrids of Polyoxometalates supported on mesoporous silica and magnetic core-shell nanoparticles for anchored homogeneous catalysis. Inorganic chemistry. Université Pierre et Marie Curie - Paris VI, 2017. English. ⟨NNT : 2017PA066300⟩. ⟨tel-01717294⟩

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