Activity Breakthrough in CO2 Photoreduction to C2H6 via Accelerated Electron Accumulation from H2O Photooxidation to H2O2.

Solar-driven CO2 reduction suffers from severe hole accumulation and inefficient electron utilization due to the sluggish kinetics of H2O oxidation to O2, thereby impeding the multi-electron C─C coupling process. This results in poor catalytic activity of C2 products. Herein, we have constructed a conjugated stacked thiophene-based supramolecular catalyst with extensive π-electron delocalization by introducing a benzene ring. This effectively promotes the oxidation of H2O to H2O2, significantly accelerating hole consumption and thereby enhancing the electron reduction reaction of CO2 at the metal center. Under illumination, the C2H6 production rate reached 101.1 µmol·g-1·h-1 with an electron selectivity as high as 98%. Compared to existing advanced systems, this represents an order-of-magnitude breakthrough in activity for C2 product synthesis. Research indicates that the enrichment of π electrons on the benzene ring of the catalyst can stabilize the H2O oxidation intermediate *OH, consuming a significant number of holes to form H2O2. This process enhances the separation and migration of photo-generated electrons at the active center and promoting the *CO-bridged C─C coupling. This significantly increases the ability to reduce CO2 to C2 products. This work provides new insights into the economic viability of photocatalytic CO2 reduction to C2H6 under pure H2O conditions.