Mechanistic Insights into Processive Polyethylene Hydrogenolysis through In Situ NMR

Chemicalpolymer upcycling by processive catalysts isa promisingplastic waste remediation strategy, with the capability of producingselective, high-value products from waste plastics with minimal energyinput. We previously designed a novel processive catalyst with a mesoporousSiO(2) shell/Pt nanoparticle/SiO2 core architecture(mSiO(2)/Pt/SiO2) that deconstructs polyolefinswithin narrow pores. Here, we elucidate the mechanism of processivepolyolefin hydrogenolysis using in situ magic-anglespinning (MAS) nuclear magnetic resonance (NMR) spectroscopy and coarse-grainedmolecular dynamics simulations. We observe that most polyethylene-Ptinteractions do not lead to C-C bond cleavage but rather tothe release of the polymer via a dehydrogenation-rehydrogenationcycle. The porous architecture increases the likelihood that a releasedpolymer is later cleaved and enables the catalyst to perform multiplesuccessive cleavages to the same polymer chain. Both experiment andsimulation show that the extent of processivity is strongly correlatedwith the length of the pores, with longer pores leading to a higherprocessivity.