Role of Framework–Carrier Interactions in Proton-Conducting Crystalline Porous Materials

Abstract

Studies of proton conductivity in crystalline porous materials (CPMs), mainly metal–organic frameworks (MOFs) and coordination polymers (CPs), have received enormous attention due to their potential application in fuel cell membranes. These materials have well-defined structural features, easy synthetic routes, and functionalizable channels. These factors provide an added advantage of their targeted synthesis and control of framework–carrier interactions that eventually determine the orderly arrangement, mobility, and density of the proton carriers. The nature of framework–carrier interactions depends on a few characteristic features such as the choice of metal ions to build the framework, the nature of the ligands, the flexibility of the framework, and the polarity of the guest molecules. This Perspective focuses on understanding the fundamental principles of proton conduction, implicates various design strategies, and discusses the role of host–guest interactions in proton conductivity, a factor largely overlooked so far.