Viologen‐Based Cationic Covalent Organic Frameworks for Efficient Dechlorination via Capacitive Deionization

ABSTRACT Advanced desalination technologies are crucial for addressing the growing global freshwater shortage crisis. Capacitive deionization (CDI) is a relatively new energy‐efficient desalination technology that has emerged in recent years. Advanced electrode materials are crucial for CDI. While research predominantly targets cathode materials for Na + capture, the equally critical challenge of chloride ion Cl − removal remains relatively underexplored, and electrode materials specifically designed for efficient chloride ion removal in CDI have received relatively little attention, limiting the progress of CDI‐based desalination technology. Here, we developed a viologen‐based cationic covalent organic frameworks (COFs)‐based active anode material exhibiting unique pseudocapacitive behavior and excellent chemical stability. Experiments demonstrate that an asymmetric electrode based on the TAPT‐BDB‐COF(Cl − )//MnO 2 (Na + ) system exhibits a low specific energy consumption of 80.70 kJ mol − 1 NaCl and maintains high capacitance retention after 500 cycles. A membrane capacitive deionization (MCDI) system assembled based on this material achieves a specific adsorption capacity of 87.2 mg g − 1 at 1.5 V and a low salt concentration of 500 mg L − 1 , increasing to 124.57 mg g − 1 at a high salt concentration of 3000 mg L − 1 . Performance remains stable after 20 desalination/regeneration cycles. This material serves as a valuable reference for the development of efficient electrode materials for capacitive deionization and chlorine removal technologies.