Molecular Iridium Complexes in Metal–Organic Frameworks Catalyze CO₂ Hydrogenation via Concerted Proton and Hydride Transfer

Molecular iridium catalysts immobilized in metal–organic frameworks (MOFs) were positioned in the condensing chamber of a Soxhlet extractor for efficient CO 2 hydrogenation. Droplets of hot water seeped through the MOF catalyst to create dynamic gas/liquid interfaces which maximize the contact of CO 2, H 2, H 2 O, and the catalyst to achieve a high turnover frequency of 410 h –1 under atmospheric pressure and at 85 °C. H/D kinetic isotope effect measurements and density functional theory calculations revealed concerted proton–hydride transfer in the rate-determining step of CO 2 hydrogenation, which was difficult to unravel in homogeneous reactions due to base-catalyzed H/D exchange.