Bioinspired iron porphyrins with appended poly-pyridine/amine units for boosted electrocatalytic CO2 reduction reaction

Developing highly efficient electrocatalysts for the CO2 reduction reaction (CO2RR) has attracted increasing interest in the past decade. Herein, we report on the design and synthesis of Fe porphyrin 1 with an appended N,N- di(2-picolyl)ethylenediamine (DPEN) unit that boosts electrocatalytic activity for CO2-to-CO conversion in acetonitrile with water as the proton source. By mimicking carbon monoxide dehydrogenase (CODH), 1 has polypyridine/amine units located at the active site to form hydrogen-bonded water-containing networks that enable fast proton transfer. The protonated and positively charged DPEN unit can also stabilize CO2 reduction intermediates through electrostatic and hydrogen-bonding interactions. These factors make 1 a highly active electrocatalyst for the CO2RR by achieving a TOFmax of 5.0 x 104 s-1 with water providing the protons. These critical roles of the DPEN unit in the CO2RR are further supported by theoretical studies. This work is significant to highlight the benefits of using molecular catalysts to elucidate structural effects.