Crown ether functionalization boosts CO₂ electroreduction to ethylene on copper-based MOFs

The electroconversion of CO₂ into ethylene (C₂H₄) offers a promising solution to environmental and energy challenges. Crown ether (CE) modification significantly enhances the C₂H₄ selectivity of copper-based MOFs, improving C₂H₄ faradaic efficiency (FE) in CuBTC, CuBDC, and CuBDC-NH₂ by 3.1, 1.7, and 2.4 times, respectively. Among these, CuBTC achieves the highest FE for C₂H₄, reaching ca. 52% at 120 mA cm⁻². Control experiments and in situ Fourier transform infrared spectroscopy (FTIR) reveal that CE stabilizes Cu⁺ during the catalyst's in situ reconstruction, promoting the formation of Cu₂O, which is more favorable for C₂H₄ production. Furthermore, CE increases the local concentration of K⁺ at the catalyst–electrolyte interface, enhancing *CO adsorption and facilitating C–C coupling reactions. This process promotes the formation of key intermediates, such as *CO*CO, *CO*COH and *COCHO, ultimately boosting C₂H₄ production.