High-efficiency electrochemical desalination enabled by nanosheet-structured redox polymer for sustainable and versatile water treatment

Hybrid capacitive deionization (HCDI) has emerged as a promising desalination technology, but its development is hindered by the lack of high-performance organic electrodes with abundant redox-active sites and robust structural stability. To address this challenge, we design a novel two-dimensional π-conjugated polymer (SFPBI) through molecular engineering, integrating multiple redox-active moieties with aromatic reinforcement strategies. Comprehensive electrochemical analysis, supported by in-situ spectroscopic characterization and theoretical calculations, reveals that SFPBI polymer, enriched with C=N and C=O functional groups, enables efficient pseudocapacitive ion adsorption. Its rigid backbone and extensive electron delocalization, characterized by a narrow HOMO-LUMO gap (2.99 eV), ensure exceptional structural stability and electrochemical activity. A HCDI device incorporating the SFPBI electrode achieves a remarkable salt removal capacity of 79.43 mg g⁻¹, a rapid average removal rate of 2.65 mg g⁻¹ min⁻¹, and excellent regeneration stability (∼92.01 % retention over 500 cycles), outperforming reported organic electrodes. As a proof of concept, we develop an integrated solar-powered desalination system using interconnected HCDI devices, which not only produces desalinated water meeting human consumption standards but also efficiently removes organic dyes and recovers energy. This study demonstrates a breakthrough in organic electrode design for HCDI, offering a scalable and energy-efficient solution for water desalination and purification.