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

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.