Decoupling Acidity from Micropore Confinement in an Amorphous–Crystalline Composite for Selective Polyolefin Waste Cracking

The persistent accumulation of polyolefin plastic waste poses a significant environmental challenge, while its sustainable conversion into valuable olefins is limited by poor accessibility and severe coking of conventional microporous zeolite catalysts. Here, we report a rationally designed amorphous-crystalline composite (ACC) catalyst that integrates short-range ordered SOD-type domains into an amorphous aluminosilicate matrix to decouple acidity from micropore confinement. This hybrid architecture provides both open diffusion channels and accessible acid sites, enabling efficient C-C bond scission while suppressing secondary reactions. In low-density polyethylene cracking at 440 °C and a catalyst-to-feed weight ratio of 10/1, the optimized ACC catalyst achieved an exceptional C₃-C₅ olefin selectivity of 94.92% and a yield of 88.08 wt %, outperforming commercial ZSM-5 and USY by factors of more than 13 and 37, respectively. The catalyst exhibited outstanding stability over 20 consecutive cycles with minimal coke formation (1.13 wt %) and broad applicability across various polyolefins and postconsumer plastic wastes. This work establishes a generalizable design strategy for decoupling acidity and mass transport in solid acid catalysts, offering a robust platform for the sustainable valorization of polyolefin waste.