Chelate Anchoring at Open Sites of Zirconium‐Oxo Cluster by Bifunctional Carboxyl‐Sulfonyl Ligand Enhancing Stability and Proton Conductivity in MOF Fibrous Membrane

ABSTRACT Developing high‐performance metal–organic framework (MOF) ‐based proton exchange membranes requires balancing proton conductivity and stability. Conventional sulfonation often compromises framework integrity by treating ‐SO 3 H groups only as proton donors. Herein, a chelate anchoring strategy uses a bifunctional carboxyl‐sulfonyl ligand that firmly binds to open metal sites on zirconium‐oxo clusters. Carboxylate groups chelate to Zr 6 ‐oxo clusters to form robust Zr 6 ‐O‐O'‐C‐CH 2 ‐SO 3 H linkages, significantly enhancing structural stability, while pendant ‐SO 3 H groups act as efficient proton carriers. Aliovalent metal substitution and dimethyl‐functionalization of the ligand further reinforce rigidity. The resulting Zr‐TPTC(Me 2 )‐SO 3 H exhibits exceptional thermal stability (827.80 K), surpassing both In‐TPTC(Me 2 ) (702.27 K) and Zr‐TPTC(Me 2 )‐SO 3 H ( 821.40 K). Well‐anchored ‐SO 3 H groups, in concert with adsorbed water, establish dense hydrogen‐bonding networks (‐SO 3 H⋯H 2 O), enabling ultrahigh proton conductivity of 6.15 × 10 −2 S cm −1 at 338 K and 95% RH, with a low activation energy (0.29 eV). Theoretical simulations corroborate enhanced water binding energy of ∆ E = ‐53.17 kcal mol −1 and extensive hydrogen‐bonding interactions that stabilize the Zr 6 clusters and facilitate efficient proton transport. Electrospinning with poly(vinyl alcohol) (PVA) yields flexible Zr‐TPTC(Me 2 )‐SO 3 H@PVA hybrid membranes, demonstrating promising practical applicability. This work provides a new paradigm for functional MOFs that transcends conventional sulfonation strategies by integrating structural reinforcement with proton conduction functionality.