Photocatalytic Asymmetric C-C Coupling for CO₂ Reduction on Cu-Zn Bimetallic Catalysts with Dipole-Limiting Effects

The photocatalytic reduction of CO₂ to multicarbon products such as ethylene remains a challenge due to the difficulty in achieving efficient C-C coupling. This study proposes a novel Cu-Zn bimetallic catalyst, CuZn-E-d-MOF, synthesized by grafting ethylenediaminetetraacetic acid (EDTA) onto a defect-rich Ti-MOF framework (d-Ti-BPDC). The catalyst exhibits excellent photocatalytic CO₂ reduction performance, with an ethylene yield of 308.72 µmol g^-1 h^-1 and an electron selectivity of 98.4%. The Cu-Zn dual sites enhance the adsorption and activation of CO₂ intermediates through asymmetric charge distribution and the formation of a dipole-limited domain field (DLDF), facilitating multi-electron transfer and C-C coupling. Density functional theory (DFT) calculations show that Cu²⁺/Cu⁺ pairs stabilize *CO intermediates and promote C─C bond formation, while Zn enhances orbital hybridization, improving electron transfer between Cu-Zn sites and *CO-*CO intermediates. In situ FTIR analysis confirms the formation of the *CO-*CO coupling intermediate, elucidating the high selectivity for C₂ products. This work highlights the role of asymmetric bimetallic sites and localized electric fields in CO₂ photoreduction, providing a promising strategy for efficient multicarbon product synthesis.