From Solvent to Catalyst: In Situ Amino Acid-Like Species Enable PET Upcycling Without Added Catalysts.

Chemical recycling of polyethylene terephthalate (PET) offers a promising route to value-added chemical production, yet conventional methods typically demand harsh conditions and dedicated catalysts. Here, we report a bioinspired strategy that exploits the intramolecular acid-base synergy of amino acids for efficient PET depolymerization. Alanine functions as a bifunctional organocatalyst, enabling complete PET esterolysis by dimethyl carbonate within 3 h at 180 °C to afford dimethyl terephthalate (98%) and ethylene carbonate (80%). Extending this concept, trace water in N-methyl -2-pyrrolidone induces in situ generation of 4-(methylamino)butyric acid, which emulates amino acid bifunctionality and enables catalyst-free depolymerization under identical conditions. Density functional theory (DFT) calculations reveal an intramolecular dual-site acid-base mechanism, where -COO- and -NH2⁺ groups cooperatively activate methanol and PET carbonyls through hydrogen-bonded cyclic transition states, lowering the barrier by ∼29 kcal mol-1. The method extends broadly to polyesters and polycarbonate, while establishing a transferable design paradigm that translates catalytic principles from nature into organocatalyst and solvent design, underscoring solvent molecular design as a general lever for sustainable catalysis and plastic upcycling.