Bio-inspired NADH regeneration by carbon nitride photocatalysis using diatom templates

In this report, the bio-inspired photocatalytic regeneration of NADH employing graphitic carbon nitride photocatalysis with a diatom frustule structure was presented. The functional structure was constructed from green and sustainable diatomite (diatom earth) by an "incipient wetness impregnation" method. By using [Cp*Rh(bpy)H₂O] ²⁺ as an electron mediator, the NADH yield can reach nearly 100%, with the enzymatically active 1,4-NADH being the only product. Furthermore, even without an electron mediator, a direct electron transfer between graphitic carbon nitride and β-NAD⁺ was possible and NADH could still be regenerated. Diatom-based carbon nitride showed a substantial improvement in regeneration efficiency compared with mpg-C₃N₄ which has a higher specific surface area. This was ascribed to the diatom structure, with its enhanced light trapping and scattering promoting high photocatalytic efficiency. Furthermore, abundant species of diatoms in the earth offer more possibilities to construct an artificial photosynthetic system using diatom frustules with excellent light-to-energy conversion efficiency.