Single-site heterogeneous catalysts for selective transformations

1) Single-site heterogeneous catalysts for oxidation reactions
2) Tuning the hydrophilic/hydrophobic character of a heterogeneous catalyst
3) Understanding the grafting and anchoring of organometallic precursors on inorganic oxides

Thanks to post-synthesis methods, it is possible to choose the most suitable catalytic centre, the optimal chemical environment, the most favourable ligands in order to design and prepare the “ideal” heterogeneous catalyst. In particular, single-site catalysts containing early transition metals show promising properties in the selective oxidation of high added-value substrates, such as fine and specialty chemicals. In our experience, titanium (IV) and niobium (V) silica-supported systems display the most interesting performance. Over these catalysts, economically and environmentally sustainable oxidants, such as organic hydroperoxides and aqueous hydrogen peroxide, can be used with good results. The hydrophilic/hydrophobic surroundings of the active catalytic centre can be modified and tuned by means of thermal treatments or silylation modifications that give rise to a surface with an optimized character to enhance the adsorption of the reactant and to favour the desorption of the desired products.

For specific applications, where a chemo-, regio- and stereo-selective catalyst is required, tailored organometallic precursors are grafted or anchored onto inorganic oxide supports with controlled geometric, morphologic and textural properties (ordered mesoporous silica materials, nanostructured inorganic oxides, clays and layered solids). In all these examples, a constant attention to the economic sustainability and to the industrial feasibility is paid.