Silica involved hierarchically porous carbon nitride for efficient NADH regeneration

Nicotinamide adenine dinucleotide (NADH) regeneration is of significant importance for the application of redox enzymes. Photocatalytic regeneration is unique for its utilization of clean and abundant solar energy. Graphitic carbon nitride (g-C₃N₄) photocatalyst has been widely applied due to its simple preparation and excellent stability. Hierarchically porous structure confers catalyst multi-functional adaptability and superiority. In this study, high-performance hierarchically porous g-C₃N₄ (HPCN) was prepared through two methods and applied in the regeneration of NADH for the first time. In one method, 300 and 7 nm SiO₂ particles were used as the hard templates and cyanamide as the precursor to fabricate HPCN-CS. When the mass ratio of two kinds of SiO₂ particles was 1:1 and the ratio of cyanamide to SiO₂ was 0.5, the catalytic activity was as high as 30.2 mM/(g·min), and the yield of NADH reached 83.7 % after 20 min, higher than that of macroporous and mesoporous g-C₃N₄. In the other method, 7 nm SiO₂ and urea were used as the dual templates to prepare HPCN-CUS together with cyanamide. When the mass percentage of cyanamide and SiO₂ was separately 10 % and 50 % of urea, the catalytic activity and the yield of NADH were 20.5 mM/(g·min) and 83.6 %, respectively.