Formylation–Decarbonylation Relay Strategy for the Selective Hydrogenation of CO2 to CO

We report here a new approach to conduct the reverse water gas shift (RWGS) reaction catalysed by a ruthenium pincer complex. In this strategy, a secondary amine is first formylated by CO2 and H2 to make H2O and formamide. The formamide then undergoes decarbonylation to produce CO with concomitant regeneration of the amine. Both steps—formylation and decarbonylation—were independently investigated through catalytic optimization studies and DFT computations at the PBE0-D3(BJ)PCM(THF)/def2-TZVP level. Using morpholine, and Ru-MACHO pincer catalyst, a TON of 249 was achieved for the hydrogenation of CO2 to CO (at 70 bar, 170°C for 90 h) with 100% selectivity.