Asymmetric Cu-N1O3 Sites Coupling Atop-type and Bridge-type Adsorbed *C1 for Electrocatalytic CO2-to-C2 Conversion

2D functional porous frameworks offer a platform for studying the structure-activity relationships during electrocatalytic CO2 reduction reaction (CO2RR). Yet challenges still exist to breakthrough key limitations on site configuration (typical M-O-4 or M-N-4 units) and product selectivity (common CO2-to-CO conversion). Herein, a novel 2D metal-organic framework (MOF) with planar asymmetric N/O mixed coordinated Cu-N1O3 unit is constructed, labeled as BIT-119. When applied to CO2RR, BIT-119 could reach a CO2-to-C-2 conversion with C-2 partial current density ranging from 36.9 to 165.0 mA cm(-2) in flow cell. Compared to the typical symmetric Cu-O-4 units, asymmetric Cu-N1O3 units lead to the re-distribution of local electron structure, regulating the adsorption strength of several key adsorbates and the following catalytic selectivity. From experimental and theoretical analyses, Cu-N1O3 sites could simultaneously couple the atop-type (on Cu site) and bridge-type (on Cu-N site) adsorption of *C-1 species to reach the CO2-to-C-2 conversion. This work broadens the feasible C-C coupling mechanism on 2D functional porous frameworks.