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

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 (Al_F) sites and migrating to T₂ Al_F 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 Al_F sites, thereby driving aluminum migration from the confined T₆-T₇ Al_F positions to accessible T₂ Al_F 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.