Fundamentals of C-O bond activation on metal oxide catalysts

Fundamental knowledge of the active site requirements for the selective activation of C-O bonds over heterogeneous catalysts is required to design multistep processes for the synthesis of complex chemicals. Here we employ reaction kinetics measurements, extensive catalyst characterization, first principles calculations and microkinetic modelling to reveal metal oxides as a general class of catalysts capable of selectively cleaving C-O bonds with unsaturation at the a position, at a moderate temperature and H-2 pressure. Strikingly, metal oxides are considerably more active catalysts than commonly employed VIIIB and IB transition metal catalysts. We identify the normalized Gibbs free energy of oxide formation as both a reactivity and a catalyst stability descriptor and demonstrate the generality of the radical-mediated, reverse Mars-van Krevelen C-O bond activation mechanism on oxygen vacancies, previously established only for RuO2. Importantly, we provide evidence that the substrate plays an equally key role to the catalyst in C-O bond activation.