Electron-mediator-free efficient photocatalytic regeneration of coenzyme NAD(P)H via direct electron transfer using ultrathin Bi2MoO6 nanosheets†

Abstract

Compared with semiconductor photocatalytic systems that utilize electron mediators for electron transfer, systems that directly transfer electrons to reaction substrates offer a cost-effective alternative, especially when avoiding the use of precious metal electron mediators. Therefore, direct electron transfer photocatalytic systems without electron mediators hold significant importance. In this study, a single-layer Bi₂MoO₆ nanosheet photocatalyst is prepared through a simple hydrothermal method. This nanosheet effectively photoreduces coenzyme NAD(P)⁺ to NAD(P)H without the need for electron mediators. When driven by the single-layer Bi₂MoO₆, the conversion of NAD⁺ reaches 64.31% within 1 hour, with a 1,4-NADH selectivity as high as 100%. Its activity and selectivity surpass most current coenzyme regeneration systems that require electron mediators. Additionally, it is found that in coenzyme regeneration systems without electron mediators, the NADH regeneration mechanism follows a typical negative hydrogen transfer pathway, divided into three steps: electron–proton–electron transfer. This study provides an effective approach for regenerating high-value coenzymes and elucidates the molecular-level mechanism of direct photocatalytic regeneration of NAD(P)H without electron mediators.