Mesoporous graphitic carbon nitride for photocatalytic coenzyme regeneration

Efficient regeneration of nicotinamide adenine dinucleotide (NADH) is of great significance for the application of oxidoreductase-catalyzed reactions. Photocatalytic regeneration is advantageous for the utilization of cheap, abundant, and clean solar energy. Graphitic carbon nitride (g-C₃N₄) has attracted wide attention due to its non-toxicity, wide range of precursors, suitable band gap, and superior chemical and thermal stability. In this work, mesoporous g-C₃N₄ (MPCN) was prepared using silica with different size as the template. The preparation process of MPCN was optimized and the effect of the template size on the structure and properties of MPCN were investigated. The results demonstrate that the smaller the template size, the larger the specific surface area of MPCN, and thus the better the photocatalytic performance. After optimization, the catalytic activity of MPCN with 7 nm silica as the template (MPCN-7) was 17.4 mM/(g min) and the NADH yield after 40 min was 70.6 %. MPCN-7 was also modified by 3-aminothiophene-2-carbonitrile (ATCN) and polyvinylpyrrolidone (PVP). Under same conditions, the catalytic activity of ATCN-MPCN, PVP-MPCN, and ATCN/PVP-MPCN was upgraded from 10.8 to 49.5, 16.4, 29.2 mM/(g min), respectively. The final yield of NADH rose from 66.9 % (40 min) to 76.3 % (12 min), 72.8 % (25 min) and 82.0 % (15 min).