Amorphous Carbon Nitride as a Robust Photocatalyst for Biocatalytic Solar-to-Chemical Conversion

Abstract

In situ regeneration of nicotinamide cofactor (NADH) is imperative because it is required as a reducing power for driving many redox enzymatic cycles useful in industry. Here, we report that amorphous carbon nitride (ACN) is a promising and robust photocatalyst for solar-driven biotransformation via NADH regeneration. Under visible light (λ > 420 nm), NADH regeneration yields by ACN reached 62.3% within an hour, whereas partially crystalline polymeric carbon nitride (CCN) hardly reduced NAD+ to NADH. Subsequently, the regenerated cofactor was consumed by l-glutamate dehydrogenase, a NADH-dependent enzyme, achieving the conversion of α-ketoglutarate with a turnover frequency of 2640 h–1. ACN showed excellent catalytic activity and long-term stability for light-driven biocatalysis; NADH regeneration efficiency after eight cycles remained above 92% of the first cycle’s efficiency, and the enzymatic reaction proceeded for more than 12 h without significant loss of ACN’s photoactivity. The remarkable photocata...