Asymmetric Molecular-Driven Aluminum Distribution and Nanocrystalline Assembly in BEA Zeolite Catalysts

Zeolites are critical materials in industrial catalysis, where optimizing both active site distribution and mass transport properties is essential for achieving high activity, selectivity, and stability. However, simultaneously controlling the aluminum site placement and porosity during zeolite synthesis remains a fundamental challenge, limiting the rational design of next-generation catalysts. In this work, we present an intentionally moderated synthesis strategy that enables concurrent tuning of aluminum distribution and hierarchical structuring in nanosized Beta (BEA) zeolite, by employing an asymmetrical organic structure-directing agent (methyltriethylammonium, MTEA+). Partial substitution of conventional TEA+ with MTEA+ leads to stronger electrostatic interactions with aluminosilicates, which decelerate nucleation, modulate Al spatial distribution, and prevent dense nanoparticle aggregation during crystallization. The resulting BEA zeolite features a loosely assembled mesoporous architecture with framework Al atoms preferentially located near the external surface and occupying T7, T1, and T2 tetrahedral sites. This dual-level control over porosity and aluminum siting enhances the catalyst performance in the methanol-to-gasoline reaction, offering an improved lifetime and hydrocarbon selectivity. Overall, our findings provide a generalizable approach to tailoring both framework architecture and active site positioning of zeolite catalysts, opening alternative pathways for the design of advanced porous materials in hydrocarbon conversion and beyond.