Lewis Acid Strength of Interfacial Metal Sites Drives CH3 OH Selectivity and Formation Rates on Cu-Based CO2 Hydrogenation Catalysts

Abstract

CH₃ OH formation rates in CO₂ hydrogenation on Cu-based catalysts sensitively depend on the nature of the support and the presence of promoters. In this context, Cu nanoparticles supported on tailored supports (highly dispersed M on SiO₂ ; M=Ti, Zr, Hf, Nb, Ta) were prepared via surface organometallic chemistry, and their catalytic performance was systematically investigated for CO₂ hydrogenation to CH₃ OH. The presence of Lewis acid sites enhances CH₃ OH formation rate, likely originating from stabilization of formate and methoxy surface intermediates at the periphery of Cu nanoparticles, as evidenced by metrics of Lewis acid strength and detection of surface intermediates. The stabilization of surface intermediates depends on the strength of Lewis acid M sites, described by pyridine adsorption enthalpies and ¹³ C chemical shifts of -OCH₃ coordinated to M; these chemical shifts are demonstrated here to be a molecular descriptor for Lewis acid strength and reactivity in CO₂ hydrogenation.

Keywords: CH3OH synthesis; CO2 hydrogenation; Lewis acids; heterogeneous catalysis; surface organometallic chemistry.