A Stable Mesoporous Zeolite with Superlarge 36-Ring Channels.

Area of Science:

• Materials Science
• Nanotechnology
• Catalysis

Background:

• Conventional organic structure-directing agents (OSDAs) limit zeolite pore size expansion beyond the microporous regime.
• Designing zeolites with larger pores is crucial for applications involving bulky molecules.

Purpose of the Study:

• To report the synthesis and characterization of a novel mesoporous pure-silica zeolite, JU-69, with exceptionally large pore apertures.
• To demonstrate a new pathway for creating crystalline mesoporous zeolites with unprecedented structural openness.

Main Methods:

• Utilized a novel surfactant-like phosphonium OSDA to direct the formation of mesoporous walls.
• Employed three-dimensional electron diffraction to determine the trigonal framework structure.
• Validated the structure using atomic-resolution electron ptychography.
• Assessed thermal stability and catalytic activity.

Main Results:

• Synthesized JU-69, a mesoporous pure-silica zeolite with 1D 36-ring channels (19.5 Å × 25.2 Å), the largest known in TO4-based frameworks.
• Achieved an ultralow framework density of 9.53 T per 1000 ų.
• Identified three composite building units (CBUs), including novel ones, forming chiral clover arrangements.
• Demonstrated thermal stability up to 900 °C and efficient metal anchoring for catalysis.

Conclusions:

• JU-69 represents a significant advancement in zeolite design, offering unprecedented pore sizes and structural openness.
• The developed OSDA and templating strategy provide a viable pathway for creating advanced crystalline mesoporous materials.
• The unique structure and properties of JU-69 enable applications in catalysis, particularly for bulky molecule hydrogenation.