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<p>We investigate the glycolysis of poly(ethylene terephthalate) or PET catalyzed by cyanamide using density functional theory. A PET dimer with C−O linkages is modeled as a representative active region. The reaction can proceed via two mechanisms based on the role of cyanamide: one involves forming a hydrogen bond with the PET dimer, while the other facilitates hydrogen transfer to promote C–O bond cleavage and O–H bond dissociation in ethylene glycol. Cyanamide stabilizes all species in the glycolysis reaction pathways by reducing their relative energies compared to the bare system. The intrinsic activation barriers for both mechanisms in the cyanamide-catalyzed system are found to be 40.6 and 36.3&#xa0;kcal/mol, respectively, both lower than the barrier observed in the bare system (42.0&#xa0;kcal/mol). We further investigate a mechanism in which cyanamide plays a dual role, simultaneously facilitating hydrogen transfer and forming hydrogen bonds with the dimer. The activation barrier is significantly reduced to 33.6&#xa0;kcal/mol compared to the single cyanamide-catalyzed systems. Hence, we suggest that cyanamide serves a dual function, promoting both hydrogen transfer for C–O bond cleavage and hydrogen bond formation with the dimer. Moreover, the electron-donating substitution on the amino group of cyanamide further enhances catalytic activity by reducing the energy barrier compared to the unsubstituted form. Finally, in the presence of a water molecule, the barrier for the dual-role mechanism is reduced to 24.8&#xa0;kcal/mol. Therefore, explicit water enhances the catalytic activity of cyanamide for PET glycolysis by acting as a medium to facilitate hydrogen transfer.</p>

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Computational study of poly(ethylene terephthalate) glycolysis catalyzed by cyanamide

  • 期刊论文

  • 发表日期：

    2025年6月14日

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  • Varangkana Jitchum,
  • Thana Maihom

摘要

We investigate the glycolysis of poly(ethylene terephthalate) or PET catalyzed by cyanamide using density functional theory. A PET dimer with C−O linkages is modeled as a representative active region. The reaction can proceed via two mechanisms based on the role of cyanamide: one involves forming a hydrogen bond with the PET dimer, while the other facilitates hydrogen transfer to promote C–O bond cleavage and O–H bond dissociation in ethylene glycol. Cyanamide stabilizes all species in the glycolysis reaction pathways by reducing their relative energies compared to the bare system. The intrinsic activation barriers for both mechanisms in the cyanamide-catalyzed system are found to be 40.6 and 36.3 kcal/mol, respectively, both lower than the barrier observed in the bare system (42.0 kcal/mol). We further investigate a mechanism in which cyanamide plays a dual role, simultaneously facilitating hydrogen transfer and forming hydrogen bonds with the dimer. The activation barrier is significantly reduced to 33.6 kcal/mol compared to the single cyanamide-catalyzed systems. Hence, we suggest that cyanamide serves a dual function, promoting both hydrogen transfer for C–O bond cleavage and hydrogen bond formation with the dimer. Moreover, the electron-donating substitution on the amino group of cyanamide further enhances catalytic activity by reducing the energy barrier compared to the unsubstituted form. Finally, in the presence of a water molecule, the barrier for the dual-role mechanism is reduced to 24.8 kcal/mol. Therefore, explicit water enhances the catalytic activity of cyanamide for PET glycolysis by acting as a medium to facilitate hydrogen transfer.