Functional Ion-Sieving Separators Based on Covalent Organic Frameworks toward Stable Aqueous Energy Storage and Conversion

Aqueous energy storage and conversion systems (AESCS) offer a cost-effective and safe alternative to conventional energy storage technologies. Among their key components, separators with high ionic selectivity are crucial for maximizing the energy output and ensuring long-term stability. Covalent organic frameworks, a class of nanoporous materials with tunable functional groups, are promising candidates for AESCS. Herein, we design and synthesize TP-4KT, which is coated onto a commercial glass fiber separator (TP-4KT@GF) to realize ion selectivity. The performance of TP-4KT@GF is evaluated in two representative AESCS: concentration cells and aqueous zinc-ion batteries (AZIBs). The modified separator achieves a high cation transference number (0.71) and a power density of 33.18 W m –2 in concentration cells, while effectively suppressing dendrite formation and improving electrochemical stability in AZIBs. This study provides valuable insights into the development of functional ion-sieving separators for next-generation energy storage and conversion technologies.