Metal-Free Carbon Nanozyme as Nicotinamide Adenine Dinucleotide Oxidase Mimic over a Broad pH Range for Coenzyme Regeneration

Exploration of high-performance nanozymes for specific biomolecules is crucial but challenging for practical application. Nicotinamide adenine dinucleotide (NADH) oxidase can drive efficient regeneration of the oxidized coenzyme NAD+, which is of great significance for numerous NAD+-dependent biocatalytic pathways. However, issues including its instability and incompatibility with tandem enzymes in terms of pH, temperature, etc. remain to be addressed. Here, we report nitrogen-doped carbon materials templated from g-C3N4 with NOX-like behaviors. The model s-NC nanozyme displays excellent catalytic activity in a wide pH range of 5.0–10.0 and a remarkable specific activity of up to 3.2 U/mg, which is superior to those of the reported NOX mimics. Furthermore, s-NC is coupled with natural dehydrogenases to develop a nanozyme–enzyme hybridization model for biosynthesis. Notably, it can well meet the pH requirement of the dehydrogenase under alkaline medium. This work not only develops NOX-mimicking metal-free nanozymes but also has inspired significance toward NAD+-mediated biosynthesis using artificial nanozymes.