Molecularly Engineered Robust Polyelectrolyte for Continuous CO ₂ Electroreduction to Pure Formic Acid

ABSTRACT Electrocatalytic CO 2 conversion to liquid fuels requires coordinated advances in catalysis and product isolation, whereas current research emphasizes the former over separation challenges essential for industrial viability. Traditional liquid electrolytes incur efficiency losses from carbonate formation, while solid‐state systems face mechanical and ionic‐transport limitations. Here, we report a mechanically resilient trimethylammonium polyelectrolyte for CO 2 ‐to‐liquid product conversion without electrolyte consumption. The molecularly aligned trimethylammonium polycations create continuous hydroxide‐conducting channels, achieving record conductivity (53 mS cm −1 , 20°C) that outperforms state‐of‐the‐art solid electrolytes. The mechanically robust polyelectrolyte maintains structural integrity and high ionic conductivity during rapid‐water‐flux operation, supporting continuous flow production of pure formic acid at a partial current density of 288 mA cm −2 in liter scale. The molecularly engineered polyelectrolytes address the catalysis and product‐separation dichotomy by enabling continuous CO 2 ‐to‐liquid‐fuel conversion and autonomous product isolation under industrial operating conditions, delivering a scalable pathway for pure liquid‐fuel‐production electrolyzers.