High intrinsic proton conduction in cerium(IV) metal-organic framework constructed by bromine-grafted terephthalic acid

Abstract

Organic linkage functionalization has been demonstrated to be an efficient approach for improving the proton conductivity of metal-organic frameworks (MOFs). Herein, we successfully synthesized a functionalized MOF, UiO-66-Br2-Ce, employing cerium(IV) ion and 2, 5-dibromoterephthalic acid (H2BDC-Br2) ligand. Since high electronegativity and hydrophilicity bromine may play a major role in boosting the proton conduction efficiency of MOFs, we thoroughly investigated the proton conductivity of this three-dimensional porous MOF. As anticipated, its optimal proton conductivity can attain 0.61 × 10−3 S cm−1 (100 °C/98% relative humidity), indicating a noteworthy enhancement in comparison to UiO-66-Ce composed only of terephthalic acid. It is also worth noting that the MOF manifested great water resistance, acid and alkali resistance, and framework stiffness during electrochemical tests, denoting exceptional structural stability. Finally, a proton-conducting mechanism based on activation energy and structural analysis was proposed.