A Light-Dark Cascade Procedure for the Regeneration of NADH using Graphitic Carbon Nitride Nanosheets

Graphical Cascading : A two-pot, light-dark cascade NADH regeneration procedure was developed. First, g-C 3 N 4 nanosheets photocatalyzed the conversion of triethanolamine (TEOA) to glycolaldehyde, which reduced NAD+ to NADH in the dark reaction step, thus avoiding the photo-deactivation of NADH. Photocatalytic regeneration of NAD(P)H is a green and promising method which utilizes clean solar energy. However, we found in this study that light exposure of NADH will cause the deactivation of the regenerated NADH. Therefore, we used ultrathin g-C 3 N 4 nanosheets as photocatalyst and developed a two-pot light-dark cascade procedure for NADH regeneration to avoid the light exposure and the deactivation of NADH. This two-pot procedure included a first light reaction step where triethanolamine was converted to glycolaldehyde through visible light photocatalysis which could reduce NAD + to NADH through a non-catalytic process in the followed dark reaction step. Using this procedure, the NADH productivity reached 1.625 mmol ⋅ h −1 ⋅ g −1 and was about 29 times higher that obtained in the one-pot method. The regenerated NADH using the two-pot procedure could act as cofactor of alcohol dehydrogenase to catalyze the reduction of acetaldehyde, illustrating the application potential of this procedure to aid enzyme catalyzed redox reactions.