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

Graphical An artificial photosystem was constructed through the covalent attachment of Rh complex onto PCN. The integrated photocatalyst could regenerate NADH efficiently by integrating the light harvesting unit and the electron transfer unit through conjugated connection. By further coupling with FDH immobilized on the hydrophobic membrane, an enhanced HCOOH production could be obtained. Natural photosynthesis is a highly unified biocatalytic system, which coupled cofactor (NAD(P)H) regeneration and enzymatic CO 2 reduction efficiently for solar energy conversion. Mimicking nature, a novel system with Rh complex covalently grafted onto NH 2 -functionalized polymeric carbon nitride (NH 2 -PCN) was constructed. The integrated connection of the light-harvesting and electron mediation modules as Rh m3 -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 CO 2 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 CO 2 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.