Carbonate-Promoted Hydrogenation of Carbon Dioxide to Multicarbon Carboxylates

CO₂ hydrogenation is a potential alternative to conventional petrochemical methods for making commodity chemicals and fuels. Research in this area has focused mostly on transition-metal-based catalysts. Here we show that hydrated alkali carbonates promote CO₂ hydrogenation to formate, oxalate, and other C₂₊ carboxylates at elevated temperature and pressure in the absence of transition-metal catalysts or solvent. The reactions proceed rapidly, reaching up to 56% yield (with respect to CO₃^2-) within minutes. Isotope labeling experiments indicate facile H₂ and C-H deprotonations in the alkali cation-rich reaction media and identify probable intermediates for the C-C bond formations leading to the various C₂₊ products. The carboxylate salts are in equilibrium with volatile carboxylic acids under CO₂ hydrogenation conditions, which may enable catalytic carboxylic acid syntheses. Our results provide a foundation for base-promoted and base-catalyzed CO₂ hydrogenation processes that could complement existing approaches.