Proton-Conductive Properties of Europium（Ⅲ）-MOF Constructed by Dibromophthalic Acid

In this study， 2，5-dibromoterephthalic acid （H₂DBTA） was employed as the organic bridging ligand， and a europium（Ⅲ）-based metal-organic framework， ［Eu2（DBTA）3（DMF）2］∙DMF （denoted as MOF 1）， was synthesized via a solvothermal method according to a reference approach. The structural features and stability of MOF 1 were systematically characterized using powder X-ray diffraction （PXRD）， Fourier transform infrared spectroscopy （FT-IR）， thermogravimetric analysis （TGA）， and scanning electron microscopy （SEM）. Pore parameters were evaluated through nitrogen adsorption-desorption measurements， while hydrophilicity was determined via water contact angle tests. Proton conductivity was investigated using alternating current （AC） impedance spectroscopy over a temperature range of 30~100 ℃ and relative humidity （RH） values of 68%~97%. The activation energy （Ea） was calculated using the Arrhenius equation to elucidate the proton transport mechanism. Results indicated that MOF 1 achieved a proton conductivity of 1.59×10-3 S/cm at 100 ℃ and 97% RH. Notably， proton transport within the MOF framework followed the Grotthuss mechanism under both high-humidity （97% RH） and low-humidity （68% RH） conditions. This work provides experimental and theoretical insights for the rational design of lanthanide-based MOFs as high-performance proton-conducting materials.