Reverse Water Gas Shift Reaction over a Homogeneous Iron Catalyst and the Underlying Mechanism

Abstract The CO production by the reverse water gas shift (RWGS) reaction is a promising bridge between CO2 conversion and well-established C1 chemistry. Currently, heterogeneous catalysts are mostly reported for this reaction, which usually require high operating temperatures (above 600 °C) and encounter poor selectivity of CO at lower temperatures (below 400 °C). Homogeneous catalysis may offer distinct advantages at a low temperature. Nevertheless, only some noble metal homogeneous catalysts for this reaction have been reported to date. Herein, we report the iron phthalocyanine (FePc) as a homogeneous catalyst to selectively produce CO via the RWGS reaction in the N,N-dimethylformamide (DMF) solvent. The reaction started at a low temperature of 120 °C with a CO selectivity of 98.1%, and high CO selectivity was attained under various conditions. Large-scale DFT calculations and control experiments revealed a tri-active-center mechanism, wherein the Fe center and Pc ligand separately and simultaneously activate CO2 and H2 and then cooperatively catalyze their conversion to CO and H2O. In addition, this work quantitatively demonstrates that the dispersion interactions between the catalyst and solvent molecules play a critical role in homogeneous transition-metal-catalyzed CO2 conversion reactions.