In situ transformation of a Bi-based MOF to a highly active catalyst for CO2 reduction

Electrochemical carbon dioxide reduction reaction (ECO2RR) is an effective means to promote carbon cycling. Recently, Bi-based metal-organic frameworks (MOFs) have attracted significant attention due to their high efficiency for formic acid generation in ECO2RR, however, their composition and morphology transformation during electrocatalysis still lack a deep exploration. Herein, a Bi-MOF with 2,4,6-tris(4-carboxyphenyl)-1,3,5-triazine (H(3)TATB) ligand is used as the prototype to investigate its in situ transformation during ECO2RR. With various characterization methods, the detailed transformation processes are revealed. Firstly, the Bi-MOF was transformed into Bi2O2CO3 due to ligand substitution in KHCO3 electrolyte, resulting in changes in both shape and composition. Secondly, during ECO2RR, the Bi3+ ions can be reduced into metallic Bi-0 nanoparticles and act as the real active component for ECO2RR. The resultant catalyst exhibits a high selectivity of up to 94.3% towards formate generation. At an optimal potential of -1.08 V vs. RHE, the catalyst can maintain a current density of -25 mA cm(-2) and a faradaic efficiency of formate over 90% for 14.5 hours. This work not only develops an efficient electrocatalyst for ECO2RR but also provides a new insight into the in situ reconstruction of MOF precursor into the active catalyst, which is useful for the design and synthesis of other materials.