Designing biomimetic catalytic systems for CO2 reduction to formate using NAD(P)H

Artificial photosynthesis refers to a synthetic method of transforming solar radiation into storable fuels that are suitable for transport and practical applications, mimicking the natural photosynthesis found in plants and algae. Successfully replicating this natural energy conversion system could represent a major breakthrough in renewable energy technology, simultaneously providing clean fuel and reducing atmospheric carbon dioxide levels. Growing concerns over excessive CO₂ emissions have led to considerable interest in developing technologies that convert CO₂ into value-added fuels and raw materials by artificial photosynthesis. Essential processes such as photon absorption, charge transfer, water splitting, NAD(P)⁺ reduction, and carbon dioxide fixation have attracted significant research interest. Nevertheless, these individual processes have predominantly been studied independently. For the combination of NAD(P)H oxidation and CO₂ reduction reactions, formate dehydrogenase (FDH) is a key enzyme in natural CO₂ recycling systems, catalysing both the oxidation of formate to CO₂ and the reduction of CO₂ to formate via electron transfer involving NAD(P)H/NAD(P)⁺. Mimicking the metal active sites of such enzymes is crucial for designing efficient catalysts for CO₂ conversion. However, no biomimetic in vivo catalysts have been reported for formate production from CO₂ using NAD(P)H. This review focuses on catalytic studies involving the conversion of CO₂ into formic acid using NAD(P)H with FDH as well as FDH-mimetic metal complexes. It covers enzymatic, photochemical, and electrochemical methods for CO₂ reduction, highlighting the structure and mechanism of FDH and recent advances in the design of FDH mimetics. Additionally, this review explores strategies for enhancing the stability of the catalyst and catalytic performance through molecular tuning, offering insights into future research directions for developing efficient and sustainable CO₂ reduction systems.