Theoretical insights into poly(ethylene terephthalate) glycolysis catalyzed by acid-base pairs in Zn-supported MOF-808 metal-organic framework

We study the polyethylene terephthalate (PET) glycolysis catalyzed by Zn-supported MOF-808, employing density functional theory. A PET dimer connected with C - O linkages is modeled as a representative PET active region. Two reaction pathways are identified: concerted and stepwise. With the contribution of Zn Lewis acid and the terminal hydroxo Lewis base at the Zr node, the stepwise pathway shows lower activation barriers, making it the preferred route. We consider the influence of the MOF-808 node, which stabilizes species along the reaction coordinates, especially transition states. We compare catalytic activity of different tetravalent metal centers of MOF-808, finding Zn-Hf-MOF808 >= Zn-Zr-MOF808 > Zn-Ti-MOF808.