3D Ordered Macroporous Cu‐Based Multimetallic Alloy Enables Efficient Asymmetric C–C Coupling for Selective CO 2 Electroreduction to Ethylene

The abundant Cu 0 /Cu δ+ interfaces generated after reconstruction are crucial for promoting the coupling of *CO and *COH intermediates in electrocatalytic CO 2 reduction. However, Cu sites derived from a single metal severely restrict C–C coupling efficiency and product selectivity. Here, the direct regulation of the interfacial microenvironment is reported by constructing a 3D ordered macroporous (3DOM) architecture composed of multimetallic alloy (MMA) on the surface of CuO x . The designed catalyst exhibits superior Faradic efficiency of 64.1% for electrochemical CO 2 reduction to ethylene at −1.55 V versus RHE under acidic conditions, and stability for over 60 h at 600 mA cm −2 in a flow cell. In‐situ experiments and theoretical simulations reveal that the 3DOM structure enhances the surface electric field, raises the local pH, and accelerates interfacial mass transport. The electronic structure of Cu δ+ (0<δ<1) sites at multimetallic interfaces is effectively regulated by other metals, inducing electronic heterogeneity and an asymmetric charge distribution on the Cu sites that facilitates asymmetric *CO–*CHO coupling. This work establishes the design principles for Cu‐based multimetallic alloy with atomic‐level customisation, demonstrating that the precise structural design and electronic structure of Cu δ+ sites could govern *CO adsorption and hydrogenation pathways, thereby enhancing ethylene selectivity.