Underevaluated Solvent Effects in Electrocatalytic CO₂ Reduction by Fe^III Chloride Tetrakis(pentafluorophenyl)porphyrin

Abstract

Fe^III chloride tetrakis(pentafluorophenyl)porphyrin (1) is known to have poor electrocatalytic activity for the CO₂ -to-CO conversion in dimethylformamide. In this work, we re-examined Fe porphyrin 1 as a CO₂ reduction catalyst in various solvents. Our results show that 1 displays fairly high electrocatalytic CO₂ -to-CO activity in acetonitrile with a turnover frequency (TOF) up to 4.2×10⁴ s^-1 . On the other hand, 1 shows a modest activity in propylene carbonate, and is inefficient to catalyze CO₂ reduction in benzonitrile, dimethylformamide, and tetrahydrofuran. Several solvent effects were considered, but none of these effects alone can explain the observed large activity difference of 1 for CO₂ reduction in these solvents. Based on the results, it is suggested that more care should be paid when comparing different CO₂ reduction catalysts because solvent effects are significant and are underevaluated.