Green Synthesis of Ultrathin MWW Zeolites With Tunable Al-T Sites Using Nitrogen-Free Secondary OSDAs for Catalytic Cracking.

The direct synthesis of ultrathin MWW zeolites with precisely controllable aluminum location represents a significant challenge. Herein, we report a sustainable approach using cycloketones as secondary nitrogen-free organic structure-directing agents (NF-OSDAs) to fabricate two-dimensional (2D) MWW zeolites. Cyclobutanone (Cy4) directs the formation of ultrathin nanosheets featuring expanded interlayer spacing and tunable aluminum distribution. We demonstrate that Na+-cycloketone complexes selectively occupy specific pore environments, effectively reducing the population of T6-T7 framework aluminum (AlF) sites and migrating to T2 AlF sites, promoting external Brønsted acidity. The resulting Cy4-MWW catalyst exhibits outstanding performance in bulky-molecule transformations. Mechanistic studies reveal that cycloketones undergo in situ self-condensation to generate dimeric species that function as pivotal structural directors. Their steric presence affects layer thickness and nanosheet packing, whereas their Na+-coordinated forms strongly interact with T2 AlF sites, thereby driving aluminum migration from the confined T6-T7 AlF positions to accessible T2 AlF sites. This strategy exhibits broad versatility across a range of cycloketones (Cy4-Cy10), enabling the concurrent tuning of both the MWW architecture and its aluminum distribution.