Depolymerization of crystalline PET under mild conditions by a serine-incorporated copper azolate hydrolase mimic

Abstract

Enzymatic hydrolysis offers a sustainable route for plastic recycling, but is limited by high costs and a strong dependence on substrate crystallinity. Herein, we report a biomimetic serine-copper azolate hydrolase mimic (CuAF(Ser)) that features a dual active site for the direct depolymerization of highly crystalline PET (38%) under mild conditions. The catalyst emulates the Lewis acid active site of carboxypeptidase through copper nodes, integrates nitrogen-containing ligands for proton transfer, and employs serine as a secondary ligand to stabilize intermediates via hydrogen bonding, creating a synergistic “metal–hydrogen bonding” mechanism. This dual-site synergy enhances PET hydrolysis by a factor of 6 compared to single-site systems. The catalyst depolymerizes highly crystalline PET (38%) under mild conditions (40 °C, pH 8) within weeks, achieving a 100% monomer yield at 60 °C in 16 days. This outperforms commercial HiC, which shows no activity toward crystalline PET under identical conditions. Furthermore, the structure–property relationship of the catalysts was unveiled by systematic regulation of the metal centers and ligand experiments, from which universal design guidelines were established. This work advances the development of mild-condition PET depolymerization and provides molecular-level insights into cooperative biomimetic catalysis.