Efficient NADH Regeneration without Electron Mediator toward Enzymatic CO₂ Reduction Enabled by a Lawn-like TP-COFs/Ti₃C₂<i>T</i>_<i>x</i> (MXene) Photocatalyst

Abstract

Photocatalytic nicotinamide adenine dinucleotide (NADH) regeneration coupled with enzymatic CO 2 reduction holds significance for global sustainable development. In this work, acrylonitrile-linked covalent organic frameworks (COFs) loaded on NH 2 –Ti 3 C 2 T x (MXene) forms a lawn-like TP-COFs/Ti 3 C 2 T x (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)(H 2 O)] 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.