Ligand-defect synergistic catalyst for localized CO2 concentration enhancement in electrochemical reduction of low concentration CO2

Electrochemical CO 2 reduction reaction (CO 2 RR) is a potential strategy for mitigating severe greenhouse effect. Despite its potential, CO 2 RR encounters critical challenges to convert low CO 2 concentrations in practical scenarios, due to the CO 2 mass transfer limitations. Herein, we prepared a reduced 2-aminoterephthalic acid modified bismuth coordination compound (Re-BiBDC-NH 2 ) for CO 2 RR in low CO 2 concentrations. Retained amino groups after in situ reduction induce abundant unsaturated coordination sites, enhancing CO 2 adsorption and enabling localized concentration enhancement even under low CO 2 supply concentrations. As such, the optimized Re-BiBDC-NH 2 achieves a Faradaic efficiency for formate (FE formate ) of > 80% at a wide potential range of 700 mV, FE formate of >75% across 15%–100% CO 2 concentrations. Furthermore, in a flow cell at a current density of 300 mA cm⁻ 2 and across a wide pH range (pH = 1.7, 7, and 14), the Re-BiBDC-NH 2 catalyst achieved FE formate > 95%, with a single-pass carbon efficiency (SPCE) reaching 71.6% in acidic electrolyte (pH = 1.7). In situ spectroscopies and Density functional theory calculations reveal that dynamically frustrated Lewis pairs formed by amino groups and defects concentrate CO 2 , and stabilize *OCHO intermediates to reduce energy barriers, thereby not only enhancing the CO 2 RR performance but also allowing reaction to operate under low CO 2 concentrations. This work presents a promising ligand-defect synergistic catalyst for low-concentration CO 2 RR, offering insights for bridging catalyst research and practical CO 2 conversion.