Regeneration of cofactor used for CO2 conversion into formate.

Abstract

Transforming CO2 into a valuable chemical compound is a promising approach toward carbon circularity. Formate is the first reduced form of CO2 and serves as a key precursor in the synthesis of various molecules. Enzyme-based CO2 conversion enables higher efficiency while reducing environmental impact (Al-Tamreh et al., 2021). A method for converting CO2 into formate using enzymes is inspired by a well-known biochemical pathway, which relies on a redox reaction between CO2 and NADH, catalyzed by formate dehydrogenases (FDH). Since NADH is expensive, its regeneration during the process is essential. In the complete CO2 conversion and NADH regeneration process, this last step can occur through hydride transfer from a reducing agent via an ion-exchange membrane. The reducing agent must be capable of regenerating the NADH without producing intermediate radical species that reduce the yield of the desired reaction, as is the case with electrochemical methods. A detailed study on potential reducing agents identified certain nicotinamides as particularly promising redox couples. This work presents the promising results of hydride exchange between NADH and certain low-cost nicotinamides, which could enable NADH to be regenerated continuously in a process for converting CO2 into formate