Efficient amine-assisted CO₂ hydrogenation to methanol co-catalyzed by metallic and oxidized sites within ruthenium clusters

Amine-assisted two-step CO2 hydrogenation is an efficient route for methanol production. To maximize the overall catalytic performance, both the N-formylation of amine with CO2 (i.e., first step) and the subsequent amide hydrogenation (i.e., second step) are required to be optimized. Herein, a class of Al2O3-supported Ru catalysts, featuring multiple activated Ru species (i.e., metallic and oxidized Ru), are rationally fabricated. Density functional theory calculations suggest that metallic Ru forms are preferred for N-formylation step, whereas oxidized Ru species demonstrate enhanced amide hydrogenation activity. Thus, the optimal catalyst, containing unique Ru clusters with coexisting metallic and oxidized Ru species, efficiently synergize the conversion of CO2 into methanol with exceptional selectivity (>95%) in a one-pot two-step process. This work not only presents an advanced catalyst for CO2-based methanol production but also highlights the strategic design of catalysts with multiple active species for optimizing the catalytic performances of multistep reactions in the future.