Engineering an Artificial Metalloenzyme for Efficient Photo-Enzymatic CO₂ Conversion

Integrated photo-enzymatic catalysis combines the merits of both photocatalytic and enzymatic systems; however, the spatial separation of photocatalysts and enzymes in conventional one-pot setups often limits overall efficiency due to sluggish electron transfer. To address this, we constructed a light-driven artificial metalloenzyme (Rh-L6-FDH) featuring dual catalytic centers by covalently conjugating formate dehydrogenase (FDH) with a tailored rhodium complex (Rh-L6), thereby facilitating synergistic NADH regeneration and CO₂ conversion. Screening nine synthesized Rh complexes with structurally diverse ligands revealed that Rh-L6 exhibited the highest efficiency for light-driven NADH regeneration. Consequently, the resulting Rh-L6-FDH conjugate yielded formate with a 2.31-fold increase compared to the physical mixture of free FDH and Rh-L6. The enhancement is mechanistically linked to the combined effects of a narrowed bandgap, diminished activation energy, and the proximity between catalytic centers, which synergistically promote charge separation and CO₂ activation. To overcome the inherent instability of the conjugate, Rh-L6-FDH was immobilized within a ZIF-67 framework. This strategy markedly improved catalytic robustness, boosting formate conversion to 98.4%-a 16.68-fold improvement over the free component system. This work demonstrates the potential of integrating molecular metal complexes with enzymes into a unified architecture, offering a promising pathway for sustainable cofactor regeneration and efficient carbon sequestration.