Sustainable Design for High‐Performance Hybrid Proton Exchange Membranes With a Proton‐Conducting Metal Organic Framework

In recent years, composite materials based on MOFs have emerged as a promising second‐generation research direction due to their potential applications in developing high‐performance, durable proton conductors, and proton exchange membranes (PEMs) for fuel cells (FCs). In this context, a novel mixed‐ligand MOF, {[Zn 2 (4‐pa)(5‐sip)(H 2 O) 3 ]·(H 2 O) 3 } n ( 1 ), has been synthesized using Zn(II) as the metal center, 4‐picolylamine (4‐pa) and sodium salt of 5‐sulfoisophthalate (5‐sip) as proton‐conducting ligands. Proton conductivity measurements revealed that compound 1 exhibits a conductivity of 3.44 × 10 −3 S.cm −1 at 80°C and 100% relative humidity. To further enhance its practical applicability, 1 was incorporated into a cost‐effective and appropriate matrix composed of a saturated polyvinylidene fluoride (PVDF) and Polyvinylpyrrolidone (PVP) mixture, forming a proton exchange mixed matrix membrane (PEMMM) referred to as 1@MMM‐XX . Notably, the 1@MMM‐XX containing 40 wt.% of 1 ( as 1@MMM‐40) demonstrated a significantly improved proton conductivity 2.81 × 10 −2 S.cm −1 under the same testing conditions. This represents nearly an 8 ‐fold and a 16 ‐fold enhancement over pure compound 1 and the blank PVDF/PVP (1.71 × 10 −3 S.cm −1 ) thin film, respectively, at 80°C, which is exceptional. The other prepared PEMMMs, for example, 1@MMM‐10 , 1@MMM‐20 , and 1@MMM‐30 , display the convincing conductivity values 2.04 × 10 −2 , 2.27 × 10 −2 , and 2.60 × 10 −2 S.cm −1 , respectively.