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.