Upcycling plastic wastes into high-performance nano-MOFs by efficient neutral hydrolysis for water adsorption and photocatalysis

Abstract

Utilizing plastic wastes as linker sources for metal–organic framework (MOF) synthesis is a green and sustainable methodology for the chemical upcycling of plastics. However, improving the depolymerization efficiency of polymers and avoiding highly corrosive solvents during the purification of the products remain significant challenges. Herein, we propose an approach to efficiently hydrolyze practical poly(ethylene terephthalate) (PET) wastes using aqueous dispersions of ultrasmall ZnO (6 nm) nanoparticles as the catalysts and subsequently synthesize five typical nano-MOFs by one-pot and two-pot strategies. The neutral hydrolysis of PET is greatly accelerated, with PET being completely depolymerized at 200 °C in 60 min with a terephthalic acid yield of 95.6%. The PET-derived MOF nanoparticles present high BET surface areas that are higher than or close to those of congeneric MOFs synthesized from petroleum-based and highly purified ligands. As a water absorbent, the two-pot MIL-101(Cr) exhibits high thermal stability with a water uptake capacity of 1327.3 mg g⁻¹. For photocatalytic degradation of antibiotic pollutants, MIL-53(Al, Fe) samples derived from PET textiles show a high tetracycline removal efficiency of over 90% within 60 min without additives in an aqueous system, outperforming most of the conventionally prepared MOF catalysts. This approach disposes of discarded plastics in an eco-friendly way and produces value-added materials with excellent catalysis and adsorption properties.