ITQ-54: a multi-dimensional extra-large pore zeolite with 20 × 14 × 12-ring channels

Area of Science:

• Materials Science
• Crystallography
• Inorganic Chemistry

Background:

• Zeolites are crucial microporous crystalline materials with diverse industrial applications.
• The synthesis of novel zeolites with unique pore structures, such as extra-large channels, remains a significant research challenge.
• Silicogermanate zeolites offer tunable properties compared to purely siliceous or aluminosilicate counterparts.

Purpose of the Study:

• To synthesize and characterize a new multi-dimensional extra-large pore silicogermanate zeolite.
• To determine the crystal structure of the novel material using advanced diffraction techniques.
• To evaluate the properties of the new zeolite, including its framework density, thermal stability, and porosity.

Main Methods:

• Synthesis of ITQ-54 via in situ decomposition of a specific organic structure-directing agent.
• Structure solution using 3D rotation electron diffraction (RED) on micron-sized crystals.
• Purification using heavy liquid separation to remove GeO₂ impurity.
• Characterization using powder X-ray diffraction (PXRD) for as-made and calcined samples.
• Assessment of thermal stability and permanent porosity.

Main Results:

• Successful synthesis of a novel silicogermanate zeolite, ITQ-54.
• Determination of a unique structure with intersecting 20 × 14 × 12-ring channels along three crystallographic axes.
• ITQ-54 exhibits one of the lowest framework densities (11.1 T atoms/1000 ų) among known zeolites.
• The material is stable up to 600 °C and retains permanent porosity after purification.
• Effective removal of GeO₂ impurity was achieved via heavy liquid separation.

Conclusions:

• ITQ-54 represents a significant advancement in zeolite chemistry, offering a rare combination of multi-directional extra-large channels and low framework density.
• The developed synthesis and purification methods provide a pathway for accessing this unique material.
• The properties of ITQ-54 suggest potential applications in catalysis, gas storage, and separation technologies requiring large pore systems.