Porous, Interface-Rich MnOx/α-Al2O3 Nanocatalyst for Chemical Upcycling of PET Plastic Waste

Abstract

Interface engineering is a pivotal strategy for achieving superior thermochemical stability and distinct acid-base and redox active sites in heterogeneous nanocatalysts. We report a morphology-controlled, porous MnOx/α-Al2O3 nanocatalyst with well-defined interfaces for efficient chemical upcycling of PET waste bottles into a high-value monomer, bis-(hydroxy neopentyl) terephthalate (BHNT), using neopentyl glycol. Electron microscopy analysis confirmed the high dispersion of MnOx nanoparticles (90 ± 10 nm) on porous α-Al2O3 nanosheets (length: 2800–5050 nm and width: 780–970 nm). This unique heterostructure combination provided intimate interfaces between MnOx and α-Al2O3, facilitating stronger acid sites (especially Lewis acidity) and Mn2+/Mn4+ active sites. The interface-rich MnOx/α-Al2O3 nanocatalyst demonstrated excellent activity in PET upcycling, yielding 90% isolated BHNT monomer. The MnOx/α-Al2O3 catalyst exhibited good reusability up to 4 cycles, with only an 8% decrease in BHNT yield. The crystal structure, morphology, porosity, and interfaces remain unchanged during the reaction, as confirmed by the spent catalyst’s analysis. The potential of the BHNT monomer was demonstrated by polyurethane synthesis, offering a truly circular plastic economy. The versatile properties and remarkable efficiency of the MnOx/α-Al2O3 nanocatalyst, along with sustainable green chemistry metrics, underscore the vital role of interface engineering in heterogeneous catalysts for the plastic recycling industry.