Synthesis of Two Structurally Distinct Cu-MOFs Regulated by Imidazole and Their Proton Conducting Properties

Developing high-performance proton conductors with robust stability remains a challenge in fuel cell technology. This study presents two copper-based metal–organic frameworks synthesized via imidazole-regulated assembly, showcasing the structural modulation effect of imidazole dosage on proton conduction properties. By adjusting the imidazole/Cu 2+ molar ratio, we obtained two distinct frameworks: Cu-DSBPDC-1D (1D chain structure with [Cu 3 (Im) 4 (COO) 2 ] clusters) and Cu-DSBPDC-2D (2D layered structure with [Cu 9 (μ 3 -OH) 6 (μ 2 -H 2 O) 4 (COO) 6 (Im) 8 ] rod-like SBUs). The 2D framework features hydrophilic channels decorated with sulfonate groups, forming continuous hydrogen-bond networks for proton transport. Both MOFs exhibit exceptional stability in boiling water and pH 3–11 solutions. Notably, Cu-DSBPDC-2D achieves a proton conductivity of 8.14 × 10 –3 S cm –1 at 85 °C and 95% RH, retaining 90% of its initial conductivity over 72 h. Isotope-effect measurements and the moderate activation energy (0.466 eV) indicate that proton transport is mediated by sulfonate-water hydrogen bonds, operating within a regime where Grotthuss and Vehicle mechanisms coexist. This work demonstrates imidazole as a dual-functional modulator for both structural assembly and proton conduction pathways, offering a rational design strategy for stable MOF-based proton conductors.