Unexpected Effect of Intramolecular Phenolic Group on Electrocatalytic CO2 Reduction

Abstract Iron porphyrin 1 with appending phenolic group was synthesized and examined as electrocatalyst for the carbon dioxide reduction (CO 2 RR). Unexpectedly, the chloride salt 1 ‐Cl is much less active as compared to iron porphyrin 2 ‐Cl, the structural analogue lacking the hanging phenolic group. By using the triflate salts, 1 ‐OTf is three times more active than 1 ‐Cl, while 2 ‐OTf displays the same activity as 2 ‐Cl for CO 2 RR. The observed trend 1 ‐OTf> 2 ‐OTf= 2 ‐Cl> 1 ‐Cl indicates that the phenolic group has both positive effect as local proton donating site and unexpected negative effect on electrocatalytic CO 2 RR.