Active-site stabilized Bi metal-organic framework-based catalyst for highly active and selective electroreduction of CO 2 to formate over a wide potential window.

Bismuth-based materials have been validated to be a kind of effective electrocatalyst for electrocatalytic CO 2 reduction (ECR) to formate (HCOO - ). However, the established studies still encounter the problems of low current density, low selectivity, narrow potential window, and poor catalyst stability. Herein, a bismuth-terephthalate framework (Bi-BDC MOF) material was successfully synthesized. The optimized Bi-BDC-120 °C exhibited excellent activity, selectivity, and durability for formate production. At an operating potential of -1.1 V vs. RHE in 0.1 mol L -1 KHCO 3 electrolyte, the ECR catalyzed by Bi-BDC-120 °C achieved a Faraday efficiency ( FE ) of 97.2% towards formate generation, and the total current density reached about 30 mA cm -2 . The operating potential window with FE formate values > 95% ranged in -0.9 to -1.5 V vs. RHE. The density-functional theory (DFT) calculation demonstrated that the (001) crystalline planes of Bi-BDC are preferable for the adsorption of CO 2 and the conversion of *OCHO intermediates, thus ultimately promoting the electrocatalytic production of formate. Although the MOF structure of Bi-BDC-120 °C was insufficiently stabilized, the FE formate could be maintained at around 90% after 36 h of ECR operation. The long-term durability for formate production was attributed to the fact that the in situ reconstructed Bi 2 O 2 CO 3 could retain the Bi-O active sites in the structure. These results offer an opportunity to design CO 2 reduction electrocatalysts with high activity and selectivity for potential applications.