Abstract Developing durable and highly conductive proton exchange membranes (PEMs) is essential for advancing electrochemical energy technologies. Leveraging fluorine‐free sulfonated polyphenylene oxide (SPPO) as membrane backbone and a multifunctionalized 2D metal–organic framework (FMOF) as fillers, composite PEM are devised with improved hydration and stability in humid conditions. The rationally optimized representative membrane SPM‐3 (3% w/w FMOF, IEC = 2.25 meq g −1 ) achieves a remarkable proton conductivity of 44.59 mS cm −1 with 835.92 mA cm −2 current density at 0.6 V, and demonstrates a significant peak power density of 629.64 mW cm −2 , which is 82% superior to the pristine SPPO at 80 °C and 100% RH. Accelerated‐degradation testing shows only 14.79% OCV decay (2.84 mV h −1 ) over 50 h at 30% RH. The fishbone‐shaped FMOF also enhances gas barrier properties, reducing hydrogen crossover by 21.7% due to blocking effect. Performance comparison with an un‐functionalized UNMOF‐based membrane confirms that free ‐COOH moieties, and heteroatoms in the FMOF create a dynamic H‐bonding web within the polyelectrolyte, resulting in compact membrane architecture, restricting water‐induced swelling and impedes the chemical degradation of the composite PEM. These findings underscore a paradigm shift to MOF‐based PEMs as a promising route toward high‐performance fuel cells.
Hossain et al. (2025) studied this question.