Fe₃O₄@ZIF-8 core–shell nanocatalysts for highly efficient and magnetically recyclable glycolysis of PET waste

In this study, magnetic core-shell Fe 3 O 4 @ZIF-8 was synthesized via a hydrothermal method and applied to Polyethylene terephthalate(PET) degradation.The catalytic degradation of PET by Fe 3 O 4 @ZIF-8 was carried out under atmospheric pressure, yielding high-value bis(2-hydroxyethyl) terephthalate (BHET) monomers.The as-synthesized Fe 3 O 4 @ZIF-8 core-shell composites possess hierarchical porosity with tunable nanoscale cavities.SEM and TEM analyses confirmed the core-shell morphology, with nanoparticles having a size distribution of 180-280 nm.The degradation product was identified as a high-purity, colorless, and transparent monomeric BHET through 1 H NMR and LC analyses.Based on a series of onefactor experiments and a Box-Behnken experimental design, the optimal process conditions were determined to be an alcoholysis temperature of 200 C, a catalyst dosage of 0.5 wt% (relative to PET mass), a reaction time of 50 min, and an ethylene glycol-to-PET mass ratio of 4.5:1.Under these conditions, the actual BHET yield reached 81.12%, closely matching the predicted value.