Upcycling PET waste into Zn-MOF integrated chitosan-PEG semi-IPN foams for rapid congo red removal with high regeneration efficiency: DFT insights into adsorption mechanism.

Plastic pollution, especially from polyethylene terephthalate (PET) waste, presents a significant environmental threat. In this study, a sustainable approach is demonstrated by upcycling PET waste into a zinc-based metal-organic framework (Zn-TPA MOF) and integrating it into a chitosan (CS)/polyethylene glycol (PEG) semi-interpenetrating polymer network (semi-IPN) to fabricate a porous composite foam via solution casting and freeze-drying. The resulting Zn-TPA@CS/PEG foam exhibits a highly porous architecture, mechanical robustness, and abundant active sites, enabling efficient dye adsorption. Characterization techniques (FTIR, XRD, SEM, BET, and TGA) confirmed the structural and chemical integrity of the composite. The foam showed an outstanding adsorption capacity of 585 mg/g for Congo Red (CR), achieving over 97 % removal within 20 min. It also exhibited strong performance in binary dye systems, with excellent selectivity and adaptability. The foam retained more than 95 % efficiency after six reuse cycles. Density functional theory (DFT) analysis confirmed the key role of MOF in adsorption, with a high binding energy of -919.55 kcal/mol, supported by hydrogen bonding and electrostatic interactions. This work presents a green and efficient strategy for transforming plastic waste into high-performance adsorbents for wastewater treatment, addressing both environmental pollution and water contamination challenges.