Post synthetic modification of Cu-MOF with riboflavin for stable electrocatalytic conversion of CO2 to formate.

Abstract

The major challenges in the development of metal-organic framework (MOF)-based electrocatalysts for CO2 reduction reaction (CO2RR) are related to their electrochemical stability, product selectivity, and electrical conductivity. To overcome these, we prepared a stable MOF-based electrocatalyst via surface functionalization of a Cu-MOF with the redox-active riboflavin (Rbf) molecule using a mechanochemical method. The modified catalyst, Rbf-Cu-MOF (1 : 1), showed three-fold higher electrocatalytic activity in the reduction of CO2 to formate than that of pristine Cu-MOF. Rbf-Cu-MOF showed the highest faradaic efficiency (FE) of 90% at -1.1 V (vs. RHE), and formate was the primary product in the reduction reaction. Post-catalytic analysis [High resolution transmission electron microscopy (HR-TEM) and X-ray absorption near-edge structure (XANES)] of the Cu-MOF samples, with and without Rbf, revealed that the Cu-MOF tended to irreversibly form Cu nanoparticles under the highly reductive electrochemical environment, while Rbf-Cu-MOF remained structurally stable for 100 h and catalytically active throughout the reaction, which can be attributed to the existence of Rbf. These findings provide vital information for employing MOF-based materials for electrocatalysis and other energy-related applications.

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