Single step, one-pot, catalyst-free upcycling of polyethylene terephthalate into biphasic carbon dots and high-purity terephthalic acid

Abstract

Polyethylene Terephthalate (PET) is a polymer widely used in the manufacture of plastic bottles, consumer-good packaging, and textile industries. Its durability and resistance to biodegradation make upcycling into high-value products challenging without harsh catalysts or extreme reaction conditions. Herein, we introduce a single-step, catalyst-free, hydrothermal process for upcycling PET into blue, fluorescent Hydrophilic (HPI) and Hydrophobic (HPO) Carbon Dots (CDs) and high-quality Terephthalic Acid (TPA). Notably, our process eliminates any need for pretreatment of the PET waste, avoiding additional multi-step procedures. The resulting HPI CDs and HPO CDs exhibit excitation-dependent emission, with peak emissions at 414 nm and 466 nm respectively. The recovered TPA demonstrates a purity of 98.5%, comparable to commercial-grade TPA, and a total TPA production yield of 72% from the maximum TPA value in PET. Our method remains effective in the presence of organic contaminants, such as food waste, as well as other plastics, including polypropylene (PP) and polyethylene (PE), mitigating the need for costly extensive waste separation.