Chitosan/ZIF-8 composite ultralight foam for efficient removal of NSAIDs and multiple dyes: Bridging collaborative adsorption and multidimensional mechanistic insights.

Effective removal of organic water pollutants is vital for ecological balance. However, achieving a universal, high-efficiency solution remains challenging. Herein, we developed a polyethyleneimine-modified chitosan/ZIF-8 ultralight foam (PCS@P-ZIF-8) that can synergistically adsorb multiple environmental contaminants, including non-steroidal anti-inflammatory drugs and cationic/anionic dyes. The ultralight foam achieved equilibrium adsorption capacities of 756.2 mg/g for diclofenac sodium, 1155.8 mg/g for Congo red (CR), 1106.0 mg/g for methyl orange, and 769.3 mg/g for sunset yellow, achieving removal rates exceeding 92 % and demonstrating excellent reusability. Through comprehensive performance evaluation, structural analysis, model fitting, and molecular simulations, we elucidated a bridge collaborative adsorption mechanism: anionic pollutants are initially captured by NH3+ groups on PCS@P-ZIF-8 foam surface, generating bridging forces that facilitate subsequent cationic dye adsorption. The multilayer adsorption model best described capture process, which was endothermic and spontaneous. Density functional theory calculations verified the bridging role of CR through electrostatic interactions, hydrogen bonding, and van der Waals forces, forming a stable ternary adsorption system (PCS@P-ZIF-8/CR/methylene blue). Toxicity tests demonstrated high biocompatibility, and the foam maintained broad-spectrum adsorption under complex water conditions, exhibiting strong anti-interference and regeneration capabilities. Overall, PCS@P-ZIF-8 shows outstanding potential for multi-pollutant water treatment, providing an effective material platform for advanced environmental remediation.