Highly stable two-dimensional bismuth metal-organic frameworks for efficient electrochemical reduction of CO2

By Fang Li, G. Gu, C. Choi, P. Kolla, Song Hong, Tai‐Sing Wu, Y. Soo, Justus Masa, S. Mukerjee, Yousung Jung and 2 more. Applied Catalysis B: Environmental, 2020

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Abstract We report a unique 2D bismuth metal-organic framework (Bi-MOF) that possesses permanent accessible porosity for efficient electrochemical CO2 reduction (ECR) to HCOOH. The 2D open-framework structure with helical Bi-O rods bridged by tritopic carboxylate ligands exhibits a remarkable Faradaic efficiency for HCOOH formation over a broad potential window, reaching 92.2 % at ∼ –0.9 V (vs. reversible hydrogen electrode, RHE) with excellent durability over 30 h. The mass-specific HCOOH partial current density is up to 41.0 mA mgBi−1, exceeding 4 times higher than that of commercial Bi2O3 and Bi sheets at ∼ –1.1 V (vs. RHE). Operando and ex-situ X-ray absorption fine structure spectroscopy revealed a structural feature associated with Bi-MOF to preserve Bi(3+) during and after long-term ECR. Theoretical calculations further showed that the crystallographically channels with abundant Bi active sites in the MOF structure favor the formation of *HCOO while suppressing the side-reaction of hydrogen evolution, thereby leading to the high selectivity for HCOOH.

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