Self-floating Cu@TpMDA@CS sponge for efficient adsorption of hexafluorobisphenol A: Enhanced recyclability and synergistic mechanisms.

Covalent organic frameworks (COFs) are promising adsorbents due to their large surface area and tunable pore structures, yet their practical application is constrained by poor recyclability and reusability. To address this issue, a self-floating Cu@TpMDA@CS sponge with a three-dimensional porous network structure was successfully fabricated by chemically crosslinking a copper-based COF (Cu@TpMDA) with chitosan (CS). This design not only facilitated recovery and practical applicability but also enabled the effective removal of hexafluorobisphenol A (BPAF) from aqueous environments. The physicochemical properties of Cu@TpMDA@CS were systematically characterized using SEM-EDS, BET, XPS, XRD, and FT-IR techniques. The adsorption performance for BPAF was evaluated through adsorption isotherm and kinetic studies, cyclic regeneration, and simulated real-water application experiments. The results showed that the adsorption of BPAF onto Cu@TpMDA@CS followed the Freundlich isotherm model and pseudo-second-order kinetic model, with a maximum adsorption capacity of 31.6 mg·g-1. Notably, the Cu@TpMDA@CS sponge exhibited excellent cyclic reusability, and after 10 adsorption-desorption cycles, its removal efficiency remained at approximately 97.0% of its initial value. The underlying adsorption mechanism was attributed to the synergistic effects of pore filling, hydrogen bond, π-π stacking, and metal coordination interactions. In conclusion, the Cu@TpMDA@CS sponge integrates favorable adsorption performance, excellent chemical stability, and superior recyclability, effectively overcoming the recovery limitations of COF-based adsorbents and demonstrating great promise as a practical candidate for wastewater treatment.