Synthesis of Sn-Incorporated Single-Walled Zeolitic Nanotube as a Lewis Acidic Catalyst

The single-walled zeolitic nanotube is a novel open-framework material distinguished by its hollow tubular morphology and double-layered zeolitic walls. Expanding its compositional diversity and tunability is crucial for unlocking the potential of this new material. Here, we report the synthesis of tin-incorporated single-walled zeolitic nanotubes (Sn-ZNT) through a solid-state ion exchange method. Owing to the unique double-layered structure, where most framework atoms are highly exposed, local dealumination is expected to occur during ion exchange using an acidic precursor, generating vacant sites for Sn substitution. Characterizations revealed that the incorporated Sn species were located at framework sites and primarily existed as partially hydrolyzed "open" sites. These Sn species enriched and strengthened the Lewis acidity, enabling Sn-ZNT to act as an efficient Lewis acidic catalyst. Using the Baeyer-Villiger oxidation as a probe reaction, Sn-ZNT exhibited remarkable activity in converting 2-adamantanone to its corresponding lactone, achieving a turnover number three times higher than that of Sn-MFI. Sn-ZNT also exhibited unexpectedly high stability, with both its structural integrity and catalytic performance preserved over multiple reaction-regeneration cycles. The successful synthesis of Sn-ZNT expands the compositional versatility of this novel material and is expected to open up new opportunities for its applications in advanced catalysis and beyond.