Dual-Defect Abundant Graphitic Carbon Nitride for Efficient Photocatalytic Nicotinamide Cofactor Regeneration

Photocatalytic regeneration of valuable cofactors by using sunlight has emerged as a promising strategy for biosynthesis and pharmaceutical manufacturing. Graphitic carbon nitride (g-C₃N₄) is very suitable for photocatalytic nicotinamide cofactor regeneration since it is metal-free, visible-light responsive and has strong binding with nicotinamide cofactor. However, its great potential is hindered by some intrinsic drawbacks such as low visible absorption, fast electron/hole recombination, and limited active sites. Here, we demonstrate dual-defect g-C₃N₄ (DDCN) with controllable defects of nitrogen vacancies and cyano groups for efficient photocatalytic cofactor regeneration via a KOH-assisted thermal polymerization by using urea as a precursor. Although DDCN is widely used for other photocatalytic applications such as organic degradation and hydrogen peroxide production, this work is original in its application to photocatalytic cofactor regeneration. Material characterizations confirm the successful introduction of nitrogen vacancies and cyano groups. Measurements of nicotinamide-cofactor generation show that the DDCN samples assisted with 0.1 g and 0.01 g KOH are 3.0 and 2.5 times that of pristine g-C₃N₄ in terms of nicotinamide cofactor yield, respectively. The high yields are attributed to the synergetic effect of both enhanced light absorption and improved charge separation, achieved through the introduction of energy levels and trap states via dual defects. This work provides a green, energy-saving, and promising strategy for nicotinamide cofactor regeneration and would promote its application in biosynthesis and drug manufacturing.