Visible‐Light Driven CO₂ Reduction to Formate with Electron Mediated Nicotinamide‐Modified Viologen in the System of Water‐Soluble Zinc Porphyrin and Formate Dehydrogenase

Abstract Visible‐light driven CO₂ reduction to formate with the system consisting of water‐soluble zinc tetraphneylporphyrin tetrasulfonate (ZnTPPS), formate dehydrogenase from Candida boidinii (CbFDH) and 1‐nicotinamidethy‐1’‐methyl‐4,4’‐ bipyridinium salt (NEMBP) in the presence of triethanolamine (TEOA) as an electron donor was investigated. NEMBP was prepared as the 4,4’‐BP with the nicotinamide‐group to promote the improvement of affinity with CbFDH. The properties of NEMBP were characterized by photochemical and electrochemical methods. In order to evaluate the affinity between cation radical of NEMBP (NEMBP^+.), as a co‐enzyme and CbFDH, the energy level based on simple docking simulation and density functional theory were estimated. It was speculated that NEMBP^+. could bind near the substrate binding pocket of CbFDH as well as NAD⁺ by docking simulation. In the visible‐light driven NEMBP reduction with the sensitization of ZnTPPS in the presence of TEOA, the yield for reduction of NEMBP to NEMBP^+. was estimated to be 80%. In the CO₂ reduction to formate with the system consisting of TEOA, ZnTPPS, NEMBP and CbFDH, the turnover numbers of NEMBP and CbFDH were estimated to be 0.14 and 1.53 h⁻¹, respectively.