Making a Splash in Homogeneous CO 2 Hydrogenation: Elucidating the Impact of Solvent on Catalytic Mechanisms

Molecular catalysts for hydrogenation of CO 2 are widely studied as a means of chemical hydrogen storage. Catalysts are traditionally designed from the perspective of controlling the ligands bound to the metal. In recent years, studies have shown that the solvent can also play a key role in the mechanism of CO 2 hydrogenation. A prominent example is the impact of the solvent on the thermodynamic hydride donor ability, or hydricity, of metal hydride complexes relative to the hydride acceptor ability of CO 2 . In some cases, simply changing from an organic solvent to water can reverse the direction of hydride transfer between a metal hydride and CO 2 . Additionally, the solvent can impact catalysis by converting CO 2 into carbonate species, as well as activate intermediate products for hydrogenation to more reduced products. By understanding the substrate and product speciation, as well as the reactivity of the catalyst towards the substrate, the solvent can be used as a central design component for the rational development of new catalytic systems.