CO2 Hydrogenation on Cu/Al2O3: Role of the Metal/Support Interface in Driving Activity and Selectivity of a Bifunctional Catalyst

Selective hydrogenation of CO₂ into methanol is a key sustainable technology, where Cu/Al₂ O₃ prepared by surface organometallic chemistry displays high activity towards CO₂ hydrogenation compared to Cu/SiO₂ , yielding CH₃ OH, dimethyl ether (DME), and CO. CH₃ OH formation rate increases due to the metal-oxide interface and involves formate intermediates according to advanced spectroscopy and DFT calculations. Al₂ O₃ promotes the subsequent conversion of CH₃ OH to DME, showing bifunctional catalysis, but also increases the rate of CO formation. The latter takes place 1) directly by activation of CO₂ at the metal-oxide interface, and 2) indirectly by the conversion of formate surface species and CH₃ OH to methyl formate, which is further decomposed into CH₃ OH and CO. This study shows how Al₂ O₃ , a Lewis acidic and non-reducible support, can promote CO₂ hydrogenation by enabling multiple competitive reaction pathways on the oxide and metal-oxide interface.