Molecular Engineering of Poly(Ionic Liquid) for Direct and Continuous Production of Pure Formic Acid from Flue Gas

Abstract Electrochemical CO 2 reduction reaction (CO 2 RR) offers a promising approach to close the carbon cycle and reduce reliance on fossil fuels. However, traditional decoupled CO 2 RR processes involve energy‐intensive CO 2 capture, conversion, and product separation, which increases operational costs. Here, we report the development of a bismuth‐poly(ionic liquid) (Bi‐PIL) hybrid catalyst that exhibits exceptional electrocatalytic performance for CO 2 conversion to formate. The Bi‐PIL catalyst achieves over 90% Faradaic efficiency for formate over a wide potential range, even at low 15% v/v CO 2 concentrations typical of industrial flue gas. The biphenyl in PIL backbone affords hydrophobicity while maintaining high ionic conductivity, effectively mitigating the flooding issues. The PIL layer plays a crucial role as a CO 2 concentrator and co‐catalyst that accelerates the CO 2 RR kinetics. Furthermore, we demonstrate the potential of Bi‐PIL catalysts in a solid‐state electrolyte (SSE) electrolyzer for the continuous and direct production of pure formic acid solutions from flue gas. Techno‐economic analysis suggests that this integrated process can produce formic acid at a significantly reduced cost compared to the traditional decoupled approaches. This work presents a promising strategy to overcome the challenges associated with low‐concentration CO 2 utilization and streamline the production of valuable liquid fuels and chemicals from CO 2 .