Electro-Driven Multi-Enzymatic Cascade Conversion of CO₂ to Ethylene Glycol in Nano-Reactor

Multi-enzymatic cascade reaction provides a new avenue for C─C coupling directly from CO₂ under mild conditions. In this study, a new pathway with four enzymes including formate dehydrogenase (PaFDH), formaldehyde dehydrogenase (BmFADH), glycolaldehyde synthase (PpGALS), and alcohol dehydrogenase (GoADH) is developed for directly converting CO₂ gas molecules to ethylene glycol (EG) in vitro. A rhodium-based NADH regeneration electrode is constructed to continuously provide the proton and electron of this multi-enzymatic cascade reaction. The prepared electrode can reach the Faradaic Efficiency (FE) of 82.9% at -0.6 V (vs. Ag/AgCl) and the NADH productivity of 0.737 mM h^-1. Shortening the reaction path is crucial for multi-enzymatic cascade reactions. Here, a hydrogen-bonded organic framework (HOF) nano-reactor is successfully developed to immobilize four enzymes in one pot with a striking enzyme loading capacity (990 mg enzyme g^-1 material). Through integrating and optimization of NADH electro-regeneration and enzymatic catalysis in one pot, 0.15 mM EG is achieved with an average conversion rate of 7.15 × 10^-7 mmol CO₂ min^-1 mg^-1 enzymes in 6 h. These results shed light on electro-driven multi-enzymatic cascade conversion of C─C coupling from CO₂ in the nano-reactor.