Regioselective Reduction of NAD⁺ to 1,4-NADH with a Bioinspired Metal Sulfide Electrocatalyst

Nicotinamide adenine dinucleotide (NAD(P)H) is an important energy carrier and charge transfer mediator in organisms. The efficient and regioselective reduction of NAD(P)(+) to NAD(P)H is of significance in biocatalysis, nature and artificial photosynthesis, but remains challenging with artificial heterogeneous catalysts. Inspired by nature oxidoreductases where active centers are transition metal sulfide clusters, here we report that CoMo2.75Sx is efficient for the regiospecific electrocatalytic reduction of NAD(+) to NADH, achieving a selectivity as high as 89 % for 1,4-NADH. It is found that the adsorbed hydrogen and hydride formed on electrode surface are crucial for the selective formation of 1,4-NADH. Based on isotopic effect, the C-H bond formation process by hydride transfer to NAD(+) is inferred to be the rate-determining step for NADH formation, which mimics enzyme catalyzed NADP(+) reduction process in nature photosynthesis.