Dual engineering of catalyst and sacrificial agent for efficient photo-biocatalytic CO2 reduction

Integrating photocatalytic cofactor regeneration with enzymatic cascades enables sustainable CO₂ valorization but faces challenges like limited hydrogen sources and homogeneous mediator and photogenerated holes-induced enzyme deactivation.

This study demonstrates that the low oxidation potential of L-ascorbic acid (L-AA) can enhance proton supply and promote the formation of [Cp*Rh(bpy)H]⁺ intermediates. Only 0.26 mg (≈ 0.12 mmol∙L⁻¹) [Cp*Rh(bpy)Cl]Cl can achieve efficient/selective reduced nicotinamide adenine dinucleotide (NADH) regeneration, which is more than twice as effective as the typical sacrificial agent triethanolamine (TEOA). A novel strategy was developed via electrostatic self-assembly of [Cp*Rh(bpy)H₂O]²⁺ onto CdIn₂S₄ microsphere photocatalysts. This innovative integration physically separated free mediators and photogenerated holes from enzymes, effectively suppressing enzyme deactivation through spatial compartmentalization. The optimal integrated photocatalytic system achieved 90% NADH regeneration efficiency within 40 min of 420 nm light irradiation, outperforming previously reported systems. When coupled with formate dehydrogenase (FDH), the integrated system achieved formic acid generation rates of 443.5 μmol·g⁻¹·h⁻¹ (one light−dark cycle) and 202.7 μmol·g⁻¹·h⁻¹ (continuous light), representing 1.2- and 3.2-fold improvements over free mediator systems, respectively. This study provides an efficient and sustainable new strategy for light driven coenzyme regeneration and enzyme catalyzed CO₂ synthesis of high value-added chemicals.