Photoenzymatic Catalytic Cascade System of a Z-Scheme Heterogeneous CdS/CN Coupled with FDH/ZIF-8 to Efficiently Regenerate 1,4-NADH for Highly Selective CO2 Reduction Toward Formic Acid

Photocatalytic regeneration of nicotinamide adenine dinucleotide (NADH) is indispensable for the sustainability of enzyme-driven industrial processes. In this study, we developed a Z-scheme heterogeneous photocatalyst consisting of CdS and g-C 3 N 4 , which markedly enhanced visible-light absorption and photogenerated charge separation efficiency, and applied it to an in situ visible-light-driven NADH regeneration system. The synthesized catalyst afforded an exceptional NADH regeneration yield of 97.88% within just 15 min. Additionally, enzyme activity assays utilizing alcohol dehydrogenase (ADH) demonstrated that 67.60% of NAD + was successfully converted into the enzymatically fraction, 1,4-NADH. Furthermore, formate dehydrogenase (FDH) immobilized on ZIF-8 was integrated into this NADH regeneration system, enabling highly sustainable biosynthesis of formic acid. During a 2 h continuous reaction, the integrated system successfully accumulated a total formic acid concentration of 0.88 mM. This novel Z-scheme photocatalytic system thus presented a highly effective solution for regenerating active NADH, providing valuable insights and promoting the development of photocatalysis-driven enzymatic systems for sustainable solar-to-chemical energy conversion. Graphical