Ion-selective covalent organic frameworks boosting electrochemical energy storage and conversion: A review

Controlling selective ion transport is highly desirable for high-efficiency energy related applications. Covalent organic frameworks (COFs) are emerging porous materials with tunable aperture sizes and diverse functional groups with charge densities similar to those of biomimetic ion channels. These merits endow COFs with excellent ion selectivity. Currently, the development of ion-selective COFs has become a focus in energy related applications; however, it faces some severe challenges. This review article systematically summarizes recent progress in the development of ion-selective COF-based materials related to the energy field. First, the structure and processes of the skeletons, linkages, and physical/chemical properties of ion-selective COFs are introduced. Second, the ion-selective mechanisms of COF-based materials are clarified based on size confinement and electrostatic interactions. Third, recent progress in the application of COFs, including lithium-ion batteries, zinc-ion batteries, and salinity gradient energy generators, is discussed. Finally, major existing challenges and potential future directions for ion-selective COF research and application are identified. This review provides a theoretical basis for the design of novel COFs with superior ion selectivity for next-generation energy related devices.