Epitaxial Bilayer MWW Zeolite with Enriched Surface Al Sites

Inside the uniform and crystalline micropores, zeolite utilizes embedded acid centers to selectively tailor chemical bonds. The catalytic performance is determined by the acid strength and abundance, accessibility, and endurance, which are challenging to realize in a single zeolite structure. Bilayer zeolite has a short diffusion distance and excellent interlayer supportive frameworks interconnected via covalent bonds. Its surface aluminum sites display significant accessibility advantages for bulky molecular catalysis. In this study, we demonstrate a direct synthesis of bilayer MWW (BL-MWW) zeolite, using hexagonal boron nitride (h-BN) as the epitaxial template seed, and hexamethylenimine (HMI) and cyclohexanone (CYCL) as the dual organic structure-directing agents. The BL-MWW zeolite displays an average of 5 nm thickness and a covalent interlayer supportive structure. Synergistically coordinated by the CYCL molecule and sodium ion, the external surface of BL-MWW exhibits an enrichment up to 11.1% of the stronger acid sites of T₂ aluminum, surpassing the 6.3% of the internal ones. The BL-MWW structure remains intact with 800 °C hydrothermal treatment and outperforms its peer zeolites in both conversion and endurance for alkylation of bulky molecules with different functionalities as well as cracking of macromolecules and polymers.