Sustainable Design for High-Performance Hybrid Proton Exchange Membranes With a Proton-Conducting Metal Organic...

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, {[Zn₂(4-pa)(5-sip)(H₂O)₃]·(H₂O)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.