Efficient NADH Regeneration without Electron Mediator toward Enzymatic CO2 Reduction Enabled by a Lawn-like TP-COFs/Ti3C2Tx (MXene) Photocatalyst

Photocatalytic nicotinamide adenine dinucleotide (NADH) regeneration coupled with enzymatic CO2 reduction holds significance for global sustainable development. In this work, acrylonitrile-linked covalent organic frameworks (COFs) loaded on NH2–Ti3C2Tx (MXene) forms a lawn-like TP-COFs/Ti3C2Tx (TCM) photocatalyst for NADH regeneration. The optimum photocatalyst TCM-15% achieves a 95% NADH regeneration yield within 30 min. More importantly, the TCM-15% obtains 46% NADH regeneration yield without an electron mediator (Cp*Rh(bpy)(H2O)2+), even higher than that of the pure TP-COFs with an electron mediator (42%). In the presence and absence of an electron mediator, the NADH regeneration TOF values of TCM-15% were 3.69 and 1.42 h–1, respectively, which were 4.05 and 4.90 times higher than those of pure TP-COFs. Subsequently, in the photoenzymatic catalytic cascade system, the formate formation rates reached 2380 and 543 μmol g–1 h–1, with and without an electron mediator, respectively. This work has laid a great foundation for achieving efficient NADH regeneration and cascade enzyme catalysis without an electron mediator.