Self-Pillared Pentasil Zeolite Microspheres as Self-Supported Catalysts With Enhanced Molecular Diffusion for Waste Plastic Upcycling.

Abstract

Hierarchical and two-dimensional zeolites often exhibit superior diffusion properties and catalytic performance unattainable with conventional three-dimensional crystals, yet their practical deployment is limited by shaping with binders that compromise these structural advantages. Here we report the synthesis of self-pillared pentasil (SPP) zeolite microspheres as self-supported catalyst bodies built from nanosheets in a characteristic house-of-cards arrangement. Time-resolved studies reveal that, in a dual-template system containing tetrabutylphosphonium hydroxide (TBPOH) and ethylenediamine (EDA) as co-structure-directing agents, SPP zeolite nanosheets spontaneously assemble into microscale spheres during crystallization while developing their hierarchical architecture. This strategy is not limited to the pure-silica composition but also enables the synthesis of aluminosilicate SPP microspheres with enriched Brønsted and Lewis acidity. Diffusion measurements, together with peak-force quantitative nanomechanical mapping (PF-QNM) and nanoindentation analyses, show that the SPP microspheres combine efficient molecular transport with appreciable mechanical robustness. As a proof of concept, we further demonstrate that the aluminosilicate SPP microspheres function as self-supported and recyclable catalysts for polyethylene upcycling, which achieve high conversion, selective formation of liquid hydrocarbons, and excellent structural stability upon reuse. These findings provide a synthetic blueprint for self-supporting structured zeolitic catalysts and highlight their broader potential in catalytic transformations involving bulky molecules.