An Artificial Co‐enzyme Based on the Viologen Skeleton for Highly Efficient CO₂ Reduction to Formic Acid with Formate Dehydrogenase

Abstract

Formate dehydrogenase (FDH) is an attractive catalyst for the reduction of CO2 because CO2 is converted to formic acid by FDH at room temperature under normal pressure in neutral aqueous solution. The reduced form of methylviologen acts as an artificial co‐enzyme for FDH in the conversion of CO2 to formic acid. To improve the catalytic activity of FDH in reducing CO2, viologen derivatives with ionic groups were synthesized as effective artificial co‐enzymes for FDH. We used enzyme kinetic analysis to assess the effect of the ionic amino or carboxyl functional groups in the reduced form of the viologen derivatives on the catalytic activity of FDH with respect to the reduction of CO2. By using 1,1′‐diaminoethyl‐4,4′‐bipyridinium salt, which is the reduced form of a viologen derivative with two amino groups, we optimized the reduction of CO2 to formic acid with FDH. The catalytic efficiency value (kcat/Km) of the reduced form of 1,1′‐diaminoethyl‐4,4′‐bipyridinium salt was estimated to be more than 560 times larger than that of the natural co‐enzyme NADH. From the analysis result, the CO2 reduction was influenced by the ionic group of the viologen derivative.

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

“…1‐Methyl‐4,4’‐bipyridinium iodide ( 2 ) was synthesized from 4,4’‐bipyridine ( 1 ) and methyl iodide according to a previous reported literature [50–53] . 1‐Aminoethtl‐1’‐methyl‐4,4’‐bipyridinium dibromide ( 3 ) was synthesized from 1‐methyl‐4,4’‐bipyridinium iodide ( 2 ) and 2‐bromoethylamine hydrobromide according to a previous reported literature [29] . Zincke salts of nicotinamide ( 5 ) was synthesized from nicotinamide ( 4 ) and 2,4‐dinitrochlorobenzene [54] .…”

“…In this system, the single‐electron reduced BPs act as a co‐enzyme for CbFDH instead of NADH. We previously reported the kinetic parameters of the single‐electron reduced various 4,4’‐ [27–30] and 2,2’‐BPs [31,32] for the CO 2 reduction to formate with CbFDH by using an enzymatic kinetic analysis. In order to elucidate the electron supply process using single‐electron reduced 4,4’‐BP as a co‐enzyme in the reduction process of CO 2 to formate catalyzed by CbFDH, moreover, the mechanism was clarified by experimental (enzyme reaction kinetics, electrochemical method) and quantum chemical analyses (docking simulation and density functional theory (DFT) calculation) [33] …”

Viologens for Coenzymes of Biocatalysts with the Function of CO2 Reduction and Utilization

“…64 Given that MV •+ effectively activates FDH, an enzymatic kinetic analysis of formic acid production from CO 2 with this enzyme in the presence of various reduced forms of 4,4¤-BP 2+ was carried out. 65,66 The conversion of CO 2 to formic acid using dithionitereduced 4,4¤-BP 2+ and FDH was conducted under the following conditions. The sample solution consisted of 4,4¤-BP 2+ (844¯M), FDH (6.4¯M), and sodium dithionite (160 mM) in a sodium pyrophosphate buffer (pH 7.4).…”

Improved Effect of Metal Coordination on Molecular Oxygen Activation for Selective Aerobic Photooxidation

“…Pyridinium materials, typically viologens, have been researched widely as the electron mediator working in photocatalytic reactions, for instance, H 2 evolution, [16,17] CO 2 reduction, [18] and ketalization reaction, [19] due to the excellent redox activity. Their derivatives with the large conjugated system also display superior sensitivity to light irradiation, which is characteristic of the photosensitizer [20] .…”