Reducing the Coordination Number of Bismuth Sites in Metal‐Organic Framework to Enhance the Performance of Electrochemical CO 2 Reduction Over a Wide Potential Range

Abstract The electrochemical CO 2 reduction reaction (CO 2 RR) to formic acid presents a promising approach for CO 2 utilization. In this work, a new Bi‐MOF ( JXUST‐302 ) with seven‐coordinated Bi nodes is constructed as the electrocatalyst for CO 2 RR. JXUST‐302 exhibits a high Faraday efficiency for HCOO – (FE HCOO– ) of 95.5% with a partial current density ( j HCOO– ) of –146.2 mA cm −2 , and FE HCOO– maintains more than 90% at a wide potential range of 700 mV. Furthermore, the FE HCOOH reaches a high value of 98.8% with j HCOOH of 92.9 mA cm −2 in the membrane electrode assembly cell with solid‐state electrolyte over 12 h for pure formic acid production. Controlled experiments suggest that the low coordination number of JXUST‐302 results in more than a three‐fold improvement in j HCOO– compared to another high coordination number of Bi‐MOF with similar structure and porosity. Mechanistic studies reveal that the lower coordination number confers an optimized electronic structure of the Bi site to lower the p‐band center while allowing the *OCHO intermediates to bind in a bridging mode, thus facilitating the reduction of CO 2 to HCOOH. This work represents an important example of regulating the coordination of catalysis to enhance the CO 2 RR performance.