Heterogeneous Metal Azolate Framework-6 (MAF-6) Catalysts with High Zinc Density for Enhanced Polyethylene Terephthalate (PET) Conversion

Polyethylene terephthalate (PET) has been extensively used for the fabrication of various packaging materials, creating million tons of waste per year. Degrading and recycling PET waste has been identified as a prominent issue. Herein, we demonstrate an effective process to chemically convert PET to bis(2-hydroxyethyl) terephthalate (BHET) through the use of metal azolate framework-6 (MAF-6) as a catalyst in the presence of ethylene glycol. MAFs are a subclass of metal–organic frameworks (MOFs), with MAF-6 comprised of the metal ion Zn2+ and the organic ligand 2-ethylimidazole. We have optimized the reaction temperature, reaction time, and catalyst amount to achieve up to a 92.4% conversion of PET and an 81.7% yield of BHET at 180 °C for 4 h. MAF-6 was easily recovered and reused for at least five times. We have also hypothesized a mechanism for the high conversion and yield of the PET glycolysis reaction catalyzed by MAF-6. The use of MAF-6 as a catalyst opens a new route for the postconsumer recycling of PET with remarkable practicality.