Integrated CO2 Capture and Conversion to Methanol Leveraged by the Transfer Hydrogenation Approach

Catalytic transfer hydrogenation of chemically captured CO2 toward MeOH production utilizing ethylene glycol as the hydride donor has been established under mild reaction conditions by employing a Ru(II)–CNN pincer catalyst (CNN = CNHC^Npyridine^Nbenzimidazole tridentate ligand) and a tertiary amine tetramethylethylenediamine (TMEDA). Through a cooperative action with ethylene glycol, TMEDA was found to be the most effective tertiary amine in this integrated CO2 capture/conversion protocol to achieve as high as 64% of MeOH yield and up to 112 catalytic turnovers. Dilute CO2 stream (10% in N2) could also be utilized in this integrated protocol to provide ∼70% yield of MeOH. Involvement of Ru–H active species in the process, generated from the reaction of the catalyst with ethylene glycol, was traced via a spectroscopic investigation. Considering that ethylene glycol can be produced from a renewable bioresource (e.g., nonfood biomass), the developed CO2-to-MeOH transfer hydrogenation protocol integrated with a prior efficient CO2-capturing process represents a prospective approach complementary to the existing catalytic hydrogenation platforms which typically use fossil-derived H2 gas under a high pressure setup.