Rh-functionalized Imino-pyridine Covalent Organic Framework Assembled on Ti3C2Tx (MXene) for Efficient NADH Regeneration and Photoenzymatic CO2 Reduction

Nicotinamide adenine dinucleotide (NADH) regeneration is crucial for sustainable enzymatic CO 2 reduction. In this study, Ti 3 C 2 T x (MXene) and [Cp*Rh(bpy)(H 2 O)] 2+ (labeled as [Cp*Rh]) were sequentially assembled onto imino-pyridine structured covalent organic frameworks (TD-COF) to construct Rh@TDM photocatalysts with dual cocatalyst. The photoelectrochemical tests and temperature-dependent photoluminescence spectra suggest that the synergistic effect of Ti 3 C 2 T x incorporation and [Cp*Rh] immobilization enables a reduction in exciton binding energy and promotes carrier transfer. Consequently, the optimized Rh 4.0 @TDM 0.15 photocatalyst achieves a 95.0% NADH regeneration yield, significantly higher than that of TD-COF with free [Cp*Rh] (32.7%). Additionally, the dual modification strategy applied to TD-COF also enhances the selectivity for 1,4-NADH. Therefore, the turnover frequency of 1,4-NADH for Rh 4.0 @TDM 0.15 achieves 1.06 h –1, which is 7.1 times higher than that of TD-COF with free [Cp*Rh] (0.15 h –1 ). Subsequently, in the photoenzymatic cascade catalytic system, Rh 4.0 @TDM 0.15 obtained a remarkable formate generation rate of 2137.7 μmol g –1 h –1 . This work not only provides a novel example of using COF containing an imino-pyridine structure to immobilize [Cp*Rh] for NADH regeneration but also reveals that the synergetic effect of MXene and [Cp*Rh] facilitates 1,4-NADH regeneration and photoenzymatic CO 2 reduction. These findings offer new insights and opportunities for the design and application of artificial photoenzymatic systems for CO 2 reduction.