Novel cationic covalent organic framework/chitosan aerogels for enhanced adsorption of diclofenac sodium: Performance and mechanism

The persistent environmental threat posed by diclofenac sodium (DCF), a low-biodegradability pharmaceutical contaminant in aquatic systems, necessitates advanced adsorbents capable of overcoming the capacity, kinetics, and recyclability limitations of conventional materials. To address this, we synthesized a novel cationic covalent organic framework/chitosan (iCOF/CS) aerogel. This was achieved first through the Schiff base condensation of 1,2,3-triaminoguanidinium chloride (TG Cl ) and 6-dihydroxynaphthalene-1,5-dicarbaldehyde (DHNDA) to form the iCOF. Subsequently, the iCOF was integrated into a chitosan matrix that was cross-linked with 1,3,5-triformylphloroglucinol (Tp), resulting in a hierarchical pore structure. The composite demonstrated exceptional DCF adsorption performance with ultrafast equilibrium within 10 min (98 % removal in 2 min) and a record capacity of 557.1 mg·g −1 , surpassing pure iCOF (473.1 mg·g −1 ) and CS aerogel (381.6 mg·g −1 ), attributed to synergistic ion exchange (Cl − /DCF − ), electrostatic attraction, π-π stacking, and hydrogen bonding, as validated by spectroscopy and theoretical calculation. The pioneering cationic COF/CS aerogel was engineered to overcome inherent recyclability limitations of powdered iCOF. The iCOF/CS aerogel gave above 97 % DCF removal in real aqueous matrices (tap, river and lake water) and over 91 % adsorption capacity after four regeneration cycles, thereby establishing a scalable remediation platform for pharmaceutical contaminants via engineered iCOF composites.