Metal–Organic Nanogel with Sulfonated Three-Dimensional Continuous Channels as a Proton Conductor
Ming Qiu, Hong Wu, Li Cao, Benbing Shi, Xueyi He, Haobo Geng, Xunli Mao, Pengfei Yang, Zhongyi Jiang
Abstract
Developing novel proton conductors is crucial to the electrochemical technology for energy conversion and storage. Metal–organic frameworks (MOFs), with a highly ordered and controllable structure, have been widely explored to prepare high-performance proton conductors. Albeit the prominent merits and great potential of the MOF-based materials such as MOF pellets or composite polymer electrolytes, constructing well-defined proton-transfer channels with much lower grain boundary resistance and more homogeneous distribution deserves extensive explorations. Herein, a kind of nanostructured metal–organic gel (MOG) with a three-dimensional (3D) interconnected proton-conductive network is prepared by a facile sol–gel method using Cr3+ and sulfonated terephthalic as the metal source and organic ligand, respectively. During the gelation process, the primary metal–organic nanoparticles are cross-linked through mismatched growth and aggregate into the 3D well-percolated gel network. The resultant MOG features in the tunable hierarchical structure and long-range continuous proton-transfer channels, leading to remarkably reduced energy barrier for proton conduction. Attributed to the sulfonated ligand and well-interconnected proton-conductive pathways, MOG exhibits intrinsic proton conductivity that is about one order of magnitude higher than that of MIL-101-SO3H pellet (MIL, Matérial Institut Lavoisier). The method in this study can be extended to construct long-range continuous ionic channels for a number of solid electrolytes.