A Bio-Inspired Bimetallic Fe−M Catalyst for Electro- and Photochemical CO₂ Reduction

The conversion of CO₂ into fuels or commodity chemicals by electrochemical or photochemical reduction is a promising strategy to relieve the ongoing energy crisis and increasing environmental pollution. Inspired by naturally occurring bimetalloenzymes, we have designed hetero–bimetallic CO₂ reduction catalysts (FeM) that involve linking an iron tetraphenylporphyrin (FeP) with a tripyridylamine (TPA) moiety, which provides a distal chelating site for Cu²⁺ or Zn²⁺. We found that the introduction of Cu²⁺ or Zn²⁺ to FeP greatly enhances its efficiency as a catalyst for the electrochemical reduction of CO₂. To gain insights into the observed synergistic effect, we performed mechanistic studies together with density functional theory (DFT) calculations. Our results show that Cu²⁺ or Zn²⁺ activates CO₂ towards reduction due to its Lewis acidity; it also functions as an oxo acceptor from CO₂. FeM also functions as an efficient catalyst for the visible-light-driven reduction of CO₂ using either [Ru(bpy)₃] Cl₂ or fac-Ir(ppy)₃ (where bpy=2,2′-bipyridine, ppy=2-phenylpyridine) as photosensitizer and 1,3-dimethyl-2-phenyl-2,3-dihydro-1H-benzo[d] imidazole (BIH) as sacrificial reductant. Again, the catalytic efficiency is enhanced by the presence of Cu²⁺ or Zn²⁺. Our results provide a general strategy for the design of a series of hetero-bimetallic catalysts for the reduction of CO₂. © 2024 Wiley-VCH GmbH.