A new Zr(IV)-based metal–organic framework, termed VNU-23 [Zr6O8(H2O)8(H2SNDC)4], where H2SNDC2− = 4,8-disulfonaphthalene-2,6-dicarboxylate, was synthesized. Subsequently, detailed structural analysis revealed that VNU-23 adopted the bcu topology with a structure characterized by densely packed sulfonic acid groups lining 6 Å channels. With this structural feature, an anchoring strategy was employed to dock the proton transfer agent, histamine, into the void space of VNU-23 to enhance the proton conductivity. Remarkably, the proton conductivity of this material reached 1.79 × 10−2 S cm−1 at 95 °C and 85% relative humidity without any appreciable loss of performance for at least 120 h.

A new Zr(IV)-based metal–organic framework, termed VNU-17 [Zr₆O₈(H₂O)₈(HSNDC)₄, where HSNDC²⁻ = 4-sulfonaphthalene-2,6-dicarboxylate], was designed to enhance proton conductivity through the incorporation of Brønsted acid functionalities. The resulting VNU-17 framework adopted the bcu topology and the structure was highlighted by densely packed sulfonic acid groups lining 6 Å channels. Following this, the internal void space of VNU-17 was engineered to further enhance proton conductivity, in which the proton transfer agent, imidazole (HIm), was anchored within the structure in two different loadings. Remarkably, the material with the highest HIm load, HIm₁₁⊂VNU-17, exhibited a 900-fold enhancement in proton conductivity (5.9 × 10⁻³ S cm⁻¹ at 85% RH and 70 °C) in comparison with the parent VNU-17 structure and was shown to maintain its performance over at least 40 h. These findings demonstrate the potential for systematically fine-tuning such materials for use as electrolyte materials in proton exchange membrane fuel cells.