Proton conductive properties of a substituted imidazole dicarboxylate-based hydrogen-bonded organic framework and a related nickel-organic framework

Abstract

The acquisition of proton conductive hydrogen-bonded organic frameworks (HOFs) and metal-organic frameworks (MOFs) has recently received sustained attention. In this paper, 2-(p-N-imidazole)phenyl-1H-4,5-imidazole dicarboxylic acid (p-IPhH3IDC) was employed to solvothermally synthesize a 3D HOF, [p-IPhH3IDC]·2H2O (1), and a 3D Ni(II) MOF, {[Ni(p-IPhH2IDC)2]·H2O}n (2). Their crystal structures have been characterized by single-crystal X-ray diffraction. By means of thermogravimetric analysis, X-ray powder diffraction, and scanning electron microscopy determinations, it was confirmed that both compounds have excellent thermal and water stability. Subsequently, their proton conductive properties were tested by AC determinations. It was found that their proton conductivities increased with the rising humidity and temperature. At 100 ​°C and 98% RH, the optimal proton conductivities are 1.06 ​× ​10−5 ​S ​cm−1 for 1 and 3.97 ​× ​10−5 ​S·cm−1for 2. Finally, the proton-conducting mechanisms of the two compounds were deduced. This work offers new inspiration for the exploration of novel proton-conductive materials.