Predicting the Activity of Single Isolated Lewis Acid Sites in Solid Catalysts

An experimental study of the activity of Ti‐, Zr‐ and Sn‐beta catalysts in different types of oxidation reactions is combined with a quantum‐chemical analysis of the electronic properties of the active sites and the adsorbed reactants. The differences observed in the catalytic behaviour of the three materials are explained in terms of the molecular orbital distribution of each system. The intrinsic Lewis acid strength of the isolated active site, the degree of back‐donation from the catalyst to the empty orbitals of the organic reactant and the net atomic charges on selected atoms are proposed as predictors of reactivity. Powerful quantum chemical calculations were combined with reaction rate measurements to elucidate the catalytic activity of Ti‐, Zr‐ and Sn‐beta zeolites for Lewis acid catalysed redox reactions. The difference in reactivity of the three materials is explained in terms of the molecular orbital distribution of the active sites and the adsorbed reactants.