Multi-enzyme reaction inspired photocatalysis for solar-driven CO₂ reduction to ethane

Photocatalytic CO₂ reduction for the production of multicarbon products has emerged as a green and sustainable technology, which shows great potential and cost-effectiveness. However, photocatalytic synthesis of two-carbon (C₂) compounds is quite challenging due to the high activation barrier of the C-C coupling reaction and low content of intermediates. Herein, inspired by the tandem synthesis in multi-enzyme reactions, Cu-N₄ and Mo-N₄ active sites have been designed and integrated in CuPor-POP-Mo as cascade dual metal sites for efficient photocatalytic reduction of CO₂ to ethane (C₂H₆) for the first time. Significantly, an excellent C₂H₆ production rate of 472.5 μmol g^-1 h^-1 and a high product selectivity of 87.5% (electron selectivity ∼97.5%) have been achieved, which are the record high values in photocatalytic C₂H₆ production by using porous polymer catalysts. In situ spectral characterization studies and DFT calculations indicate that the Cu site enhanced the localized surface coverage of *CO on CuPor-POP-Mo, while the Mo site of the photocatalyst triggered the C-C coupling of *CO intermediates, and the energy barrier of which was synergistically lowered by Cu and Mo sites, resulting in highly effective C₂H₆ production. This work develops novel metal sites for ethane production and enables precise modulation of *CO intermediate coverage to decrease the energy barrier for *OCCO generation, thus opening a new pathway for highly selective photocatalytic CO₂ reduction toward value-added chemicals and fuels.