Tailoring Polymeric Binder of Permselective Gas Diffusion Electrode for Low‐Concentration CO₂ Electrolysis

Electrochemical CO 2 reduction (eCO 2 R) offers a promising route to convert industrial CO 2 emissions into value‐added chemicals. However, direct electrolysis of low‐concentration CO 2 streams from flue gas suffers from mass transport limitation, resulting in poor Faradaic efficiency (FE). To address this challenge, a gas diffusion electrode featuring a permselective layer is developed that selectively concentrates CO 2 at the catalyst interface. The permselective layer integrates a hybrid CO 2 ‐philic metal‐organic framework Calgary Framework‐20 (CALF‐20) filler embedded within a tailored polymer matrix. Three polymers—Nafion, polysulfone (PSF), and styrene‐ethylene‐butylene‐styrene—as the polymer matrix to optimize CO 2 /N 2 selectivity and permeability are systematically tested. The CALF‐20/PSF composite in the permselective layer achieves a CO 2 /N 2 selectivity of ≈40, enabling a threefold increase in CO partial current density ( j CO of −42.7 mA cm −2 ) with a dilute CO 2 feed (10 volume percentage) compared to unmodified electrodes at an applied current density of −50 mA cm −2 . In a membrane electrode assembly, the optimized electrode maintains a stable FE CO of ≈70% for over 20 h. CO 2 uptake studies and structural characterization reveal that strong interactions between the triazole ligands of CALF‐20 and the sulfonyl/ether groups of PSF enhance both CO 2 transport and electrode durability.