Mild-Condition Upcycling of Polyolefins Enabled by Micropore Confinement in Zeolites.

The catalytic upcycling of polyolefin waste into valuable chemicals offers a sustainable strategy to mitigate plastic pollution and advance resource sustainability. Selectively cracking the inert C─C bonds in polyolefins under mild, co-reactant-free conditions remains a fundamental challenge due to their chemical stability and poor diffusivity. Herein, we report a co-reactant-free strategy for the selective cracking of polyolefin into C2-C6 olefins at 240 °C under 1 atm N2, enabled by b-axis-shortened HZSM-5 nanosheet zeolites (s-ZSM-5) with tailored micropore confinement and acidity. Mechanistic investigations reveal an isomerization-oligomerization-scission (IOS) cycle confined within zeolite micropores, which arises from the synergistic interplay of controlled confinement and diffusion. This dynamic cycle is driven by the preferential diffusion of short-chain olefins, which disrupts local reaction equilibrium and drives continuous cracking. The optimized s-ZSM-5 catalyst achieves up to 94.7% low-density polyethylene (LDPE) conversion and 90.0% C2-C6 olefin selectivity, while exhibiting exceptional coking resistance and compatibility with diverse post-consumer plastics. These findings establish a novel mechanistic foundation for confined-space effect and offer guiding principles for the rational design of solid catalysts for sustainable plastic upcycling.