A hexacoordinated Bi3+-based ellagate MOF with acid/base resistance boosting carbon dioxide electroreduction to formate

Abstract

Electrochemical conversion of CO₂ into energy-dense liquids, such as formic acid, as hydrogen carriers and chemical feedstocks is desirable. However, the development of highly efficient and stable electrocatalysts toward formate production in a wide potential window still remains a great challenge. Herein, rod-shaped bismuth ellagate metal–organic framework (referred to as SU-101) catalysts were demonstrated to exhibit excellent activity, selectivity, and stability for the conversion of CO₂ into HCOO⁻. In particular, the SU-101 nanorods (NRs) achieved a high HCOO⁻ Faraday efficiency (FE) up to 93.66% at −1.10 V vs. RHE and a partial current density of −14.57 mA cm⁻². Significantly, the FE of HCOO⁻ could be maintained over 87.51% during 10 hours of continuous electrolysis without significant deterioration. The results indicated that the excellent performance could be attributed to the special structure of Bi₂O(H₂O)₂(C₁₄H₂O₈)·nH₂O (SU-101). DFT calculations show that the unique hexacoordinated Bi³⁺ site of SU-101 is highly efficient for formate production with very low overpotentials. This work paves a way to develop a Bi-MOF as a highly stable, molecularly tunable catalytic material for selective CO₂ reduction to specific valuable chemicals.