Surface Engineered 2D‐β‐ketoenamine Covalent Organic Framework for Superior Dechlorination via Hybrid Capacitive Deionization

Abstract

Abstract To prevent a global water shortage crisis, we must innovate to desalinate seawater. Hybrid capacitive deionization (HCDI), an energy‐efficient desalination method, depends on electrode materials. Removing chloride ions (Cl − ), a key salinity factor, is vital for balanced electrode capacity. Yet, efforts focus mainly on cathode materials for Na + capture, limiting the progress of electrochemical desalination. Herein, we have developed a covalent organic framework (COF)‐based redox‐active anode material with excellent chemical stability and unique pseudocapacitive behavior. In the HCDI cell, the rationally designed material showed a remarkable chloride ion removal capacity (Cl‐RC) of 71.5 mg g −1 in 1300 ppm saline solution with a noteworthy removal capacity rate (Cl − RCR) of 1.85 mg g −1  min −1 , while maintaining 98.7% capacity retention over 30 cycles. Under optimized conditions, the COF electrode displayed a high selectivity toward Cl − over other anions present in real‐seawater samples with Cl‐RC of 89 mg g −1 , implying its practical applicability. To the best of our knowledge, this work represents the first example of a purposefully functionalized COF serving as an anode in HCDI, highlighting the promising role of COFs in advancing capacitive deionization technologies.