Another way of coupling molecular and solid catalysis is to develop homogeneous molecular catalysts (organometallic complexes) and graft them onto the surface of a solid support, preferably transparent and conductive if the aim is to produce catalysts for photo- or electro-catalysis. Grafting a molecular catalyst onto a solid can have many advantages: (i) stabilization of the catalyst; (ii) more efficient electron transfer; (iii) limitation of bimolecular deactivation processes; (iv) greater concentration of the catalyst in the reaction layer; (v) fewer limitations by diffusion of active species; (vi) better exploitation of the catalyst atoms; (vii) possibility of exploitation in practical technological devices; (viii) recycling recovery of the catalyst. There are also disadvantages: (i) need to modify the catalyst, which can be costly and can change the reactivity of the catalyst; (ii) more delicate structural, electrochemical and mechanistic characterization of the "molecular" material (before and after reaction); (iii) low density of active sites.
This lecture presents in detail the different technologies for covalent or non-covalent grafting of molecules onto a solid, as well as significant examples of heterogenized molecular catalysts for proton reduction to hydrogen, water oxidation to oxygen, oxygen reduction to water andCO2 reduction to formic acid, CO and hydrocarbons, including work carried out at the Collège de France's " Chemistry of Biological Processes Laboratory ".
