Bioinspired Photocatalytic NADH Regeneration by Covalently Metalated Carbon Nitride for Enhanced CO2 Reduction

Natural photosynthesis is a highly unified biocatalytic system, which coupled cofactor (NAD(P)H) regeneration and enzymatic CO2 reduction efficiently for solar energy conversion. Mimicking nature, a novel system with Rh complex covalently grafted onto NH2 -functionalized polymeric carbon nitride (NH2 -PCN) was constructed. The integrated connection of the light-harvesting and electron mediation modules as Rhm3 -N-PCN could promote the efficient NAD+ reduction to NADH. As a result, the integrated system exhibited a conversion of ∼66 % within 20 minutes. By further coupling in situ generated NADH with formate dehydrogenase (FDH), a photoenzymatic production of formic acid (HCOOH) from CO2 was accomplished. Moreover, by immobilizing FDH onto a hydrophobic membrane, an enhanced HCOOH production of ∼5.0 mM can be obtained due to the concentrated CO2 on the gas-liquid-solid three-phase interface. Our work herein provides an integrated strategy for coupling the anchored electron mediator with immobilized enzyme for enhanced artificial photosynthesis.