Overcoming Hydrophobicity with Water Enables Ultrafast Hydrolysis of Waste Polyethylene Terephthalate at Very Mild Conditions

Chemical recycling of plastics holds great promise but remains constrained by sustainability issues, with polyethylene terephthalate (PET) epitomizing this challenge. Herein, we introduce a conceptually novel strategy that overcomes PET's intrinsic hydrophobicity by physically re-engineering the polymer's microstructure to enable ultrafast alkaline hydrolysis under exceptionally mild conditions. We leverage the ability of propylene carbonate (PC)-an inexpensive, commercial, green solvent-to selectively dissolve PET, to thermally induce phase separation, and subsequently act as a carrier for water insertion between polymer chains. Upon complete PC replacement, the water uptake exceeds twice the polymer mass, preventing chain re-compaction and establishing an interfacial environment that facilitates hydroxyl ion diffusion to ester bonds and depolymerization with minimal alkali consumption. As a result, water-swollen PET fully depolymerizes (96% TPA yield) at atmospheric pressure within 5 min at 90 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:semantics> <mml:mrow><mml:msup><mml:mrow></mml:mrow> <mml:mo>∘</mml:mo></mml:msup> <mml:mi>C</mml:mi></mml:mrow> <mml:annotation>$^{\circ }{\rm C}$</mml:annotation></mml:semantics> </mml:math> or under 2 h at room temperature, vastly outperforming conventional hydrolysis methods. The process achieves a <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:semantics><mml:mo>></mml:mo> <mml:annotation>$>$</mml:annotation></mml:semantics> </mml:math> 20-fold reduction in energy footprint versus direct PET hydrolysis. It performs robustly on challenging, real-world feedstocks-including textiles and mixed plastic waste-enabling selective depolymerization unaffected by PET crystallinity. A techno-economic analysis (TEA) confirms energy efficiency and strong economic feasibility, demonstrating overall competitiveness with existing engineered technologies. Beyond PET, the physical mechanism underpinning the strategy offers a scalable and sustainable platform for recycling a wide range of condensation polymers.