Insights into Structural Details of Zeolites Via Three-Dimensional Electron Diffraction

Zeolites and related microporous materials have been widely used as absorbents, ion-exchangers, selective catalysts, etc. The unique properties of zeolites are associated with their well-defined pores and channels of molecular dimensions. Because of the close structure-property relationship, numerous efforts have been made to synthesize zeolitic materials with new pore structures and compositions and subsequently exploit their applications. Therefore, a crucial part in the study of zeolitic materials is to reveal their atomic structures and underlying properties.

X-ray diffraction method has been routinely applied for structural determination of crystalline materials. However, challenges remain on the structural analysis of nanocrystalline materials which are too small to be studied by single crystal X-ray diffraction (SCXRD). Powder X-ray diffraction are the alternatives. Nevertheless, additional challenges rise due to peak overlapping.

By taking the advantages of the short wavelength of electron, three-dimensional electron diffraction (3DED) has been developed to meet these challenges^1,2, and it has been used for structural analysis of complex zeolites³. For example, one of the most complicated zeolitic structures, PST-5, has been determined by 3DED recently. Notably, only by using 3DED, we can discover and fundamentally understand the unique 3D-3D topotactic transformation, which takes advantage of weak bonding in PST-5, and transforms to PST-6⁴. By adopting the transformation, it could open a new way for synthesis of targeted zeolites, especially those which may not be feasible by conventional methods.

(1) Wan, W.; Sun, J.; Su, J.; Hovmöller, S.; Zou, X. J. Appl. Crystallogr. 2013, 46, 1863.

(2) Huang, Z.; Ge, M.; Carraro, F.; Doonan, C.; Falcaro, P.; Zou, X. Faraday Discuss. 2021, 225, 118.

(3) Huang, Z.; Willhammar, T.; Zou, X. Chem. Sci. 2021, 12, 1206.

(4) Huang, Z.; Seo, S.; Shin, J.; Wang, B.; Bell, R. G.; Hong, S. B.; Zou, X. Nat. Commun. 2020, 11, 3762.