Ab initio structure determination of interlayer expanded zeolites by single crystal rotation electron diffraction.

Area of Science:

• Materials Science
• Crystallography
• Chemistry

Background:

• Layered solids often form small crystals unsuitable for single-crystal X-ray diffraction.
• Powder X-ray diffraction (PXRD) is limited by peak broadening and overlapping for these materials.

Purpose of the Study:

• To demonstrate the ab initio structure determination of two interlayer expanded zeolites, COE-3 and COE-4.
• To showcase the utility of the rotation electron diffraction (RED) method for submicron-sized crystals.

Main Methods:

• Utilized software-based rotation electron diffraction (RED) for automated 3D electron diffraction data collection and processing.
• Collected RED datasets from multiple electron-beam sensitive crystals.
• Performed Rietveld refinement against powder X-ray diffraction (PXRD) data for structure refinement.

Main Results:

• Successfully determined the ab initio structures of COE-3 and COE-4 zeolites.
• COE-3 and COE-4 feature ferrierite-type layers pillared by specific siloxane linkers.
• Structures possess intersecting 10-ring channels parallel to the layers.

Conclusions:

• Rotation electron diffraction (RED) is effective for ab initio structure determination of small, layered crystalline materials.
• The method complements and refines results obtained from powder X-ray diffraction (PXRD).
• Established the detailed structures of two novel microporous silicates, COE-3 and COE-4.