One–step aqueous synthesis of Mn– ZnO : Mitigating enthalpy–entropy trade–off for atom–economical PET upcycling

Abstract

Overcoming the enthalpy–entropy compensation effect remains a formidable challenge in chemical upcycling of polyesters. Empirical catalyst designs typically maximize Lewis acidity, lowering activation enthalpy (Δ H ‡) for ester activation but triggering an entropic penalty (Δ S ‡) that retards kinetics. Here, we establish a “moderate acidity” principle that balances these competing thermodynamic demands. Eyring analysis shows that optimal 5% manganese (Mn) doping enables a substantial reduction in Δ H ‡ while mitigating the entropic penalty. Mn‐doped zinc oxide (ZnO) catalysts prepared via microfluidic synthesis achieve optimal performance at 5% Mn doping, delivering 100% PET conversion, 94.7% BHET yield, and a space–time yield of 250 g _monomer  g _cat ⁻¹  h ⁻¹ , twice that of pristine ZnO. Life‐cycle and techno‐economic assessments demonstrate 3.7‐fold lower greenhouse gas emissions and 2.4‐fold cost reduction relative to conventional routes. Complete atomic utilization is achieved by valorizing glycolysis mother liquor into high‐performance waterborne polyurethanes, establishing a zero‐waste circular economy for plastics.