Proton Conduction in Metal-Containing Supramolecular Polymers and Hybrid Materials: Recent Advance and Future...

Among various alternative renewable energy resources, the proton exchange membrane fuel cell (PEMFCs) is considered a promising one. Proton exchange membrane (PEM) that serves as an inevitable part of PEMFCs requires to have high proton conductivity and minimum electrical conductivity. Until now, different organic, inorganic, and hybrid crystalline materials, such as coordination polymers (CPs), polyoxometalates (POMs), metal-organic frameworks (MOFs), covalent organic frameworks (COFs), and hydrogen-bonded organic frameworks (HOFs), have been explored as PEM materials. However, poor processability and high crystallinity of these materials hinders easy membrane fabrication. In this regard, recently, immense research interests have been given toward exploring metal-based supramolecular polymers with high processability, durability, and stimuli-responsive properties as PEM in fuel cell. However, till date, no comprehensive review has been published focusing on proton conductivity of different metal-based supramolecular materials. This review aims to highlight the progress achieved in last 12 years on metal-based supramolecular polymers and soft hybrid materials as efficient proton conductor for potential application in PEMFCs. The article not only highlights the key design strategies and the fundamental structure property correlations for achieving high proton conduction in supramolecular materials, but also points out the challenges and future prospects.