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

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 in 1300 ppm saline solution with a noteworthy removal capacity rate (Cl RCR) of 1.85 mg g min, 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, 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.