The proposed structure of the immobilized ruthenium catalyst synthesized in situ during the carbon dioxide hydrogenation to formic acid, the activation of carbon dioxide and the possible reaction mechanism were discussed. In the reaction, a phosphine ligand in the Ru complexes was replaced by protonic solvent ROH to generate the chain carrier, subsequent normal insertion of carbon dioxide into the Ru—H bond occurred to give the formato complex. Then hydrogenolysis of the Ru-O₂CH bond formed formic acid and regenerated the catalytic species to finish the catalytic cycle.

Key words: immobilized, formic acid, Ru-based catalyst