Performances of catalysts and more generally of devices is mainly controlled by our ability to generate specific sites/objects (organometallic complexes, nanoparticles, uniform thin films…) onto supports (powders or flat surfaces). In this context, we have developed a rational approach to yield functional materials containing well-defined surface-active sites. This approach is based on the understanding of the molecular reactivity of molecules/objects onto surfaces and a strong effort is directed towards the elucidation of surface sites’ molecular structures. In this context, we have developed synthetic methods allowing the preparation of well-defined heterogeneous catalysts containing highly active metallo-N-heterocyclic carbene complexes (M-NHC). The materials were fully characterized using several techniques and in particular by advanced solid state NMR using Dynamic Nuclear Polarization (SENS-DNP) which allowed the molecular description of surface Metallo-NHC sites. Different M-NHC (M = Ru, Ir, Pd…) based catalysts were tested in selective hydrogenation (Ir), olefin metathesis (Ru), CO2 reduction (Ru) and the Z-selective semi-hydrogenation of alkynes (Pd). Their performances were compared to those of homogeneous homologues in solution. In the worst cases, the materials were found as active as homogeneous counterparts. In the best cases, the developed systems were more than 50 times more active (in term of rate and TON). These remarkable performances were attributed to surface site isolation which suppresses bimolecular deactivation processes and to beneficial interactions between the silica surface and the M-NHC.

Combining surface organometallic chemistry and advanced solid-state NMR techniques (SENS-DNP) allows yielding and understanding molecular single site catalysts

255th National Meeting (2018)

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