Mechanistic Insights into Processive Polyethylene Hydrogenolysis through<i>In Situ</i>NMR
Yunpu Zhao, Max Meirow, Akalanka Tennakoon, Xun Wu, Alexander L. Paterson, Long Qi, Anne M. LaPointe, Jessica V. Lamb, Takeshi Kobayashi, Massimiliano Delferro, Aaron D. Sadow, Wenyu Huang, Erik Luijten, Frédéric A. Perras
Abstract
Chemical polymer upcycling by processive catalysts is a promising plastic waste remediation strategy, with the capability of producing selective, high-value products from waste plastics with minimal energy input. We previously designed a novel processive catalyst with a mesoporous SiO 2 shell/Pt nanoparticle/SiO 2 core architecture (mSiO 2 /Pt/SiO 2 ) that deconstructs polyolefins within narrow pores. Here, we elucidate the mechanism of processive polyolefin hydrogenolysis using in situ magic-angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy and coarse-grained molecular dynamics simulations. We observe that most polyethylene–Pt interactions do not lead to C–C bond cleavage but rather to the release of the polymer via a dehydrogenation–rehydrogenation cycle. The porous architecture increases the likelihood that a released polymer is later cleaved and enables the catalyst to perform multiple successive cleavages to the same polymer chain. Both experiment and simulation show that the extent of processivity is strongly correlated with the length of the pores, with longer pores leading to a higher processivity.