Ordered silicon vacancies in the framework structure of the zeolite catalyst SSZ-74

• Published in: Nature materials Vol. 7; no. 8; pp. 631 - 635
• Main Authors: McCusker, Lynne B, Baerlocher, Christian, Xie, Dan, Hwang, Son-Jong, Chan, Ignatius Y, Ong, Kenneth, Burton, Allen W, Zones, Stacey I
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 01.08.2008; Nature Publishing Group
• Subjects: Algorithms; Biomaterials; Catalysts; Chemistry and Materials Science; Condensed Matter Physics; Electron microscopy; letter; Materials Science; Nanotechnology; Optical and Electronic Materials; Petrochemicals; Porous materials; Silica; Zeolites
• ISSN: 1476-1122; 1476-4660
• DOI: 10.1038/nmat2228

Physico-chemical characterization of the high-silica zeolite catalyst SSZ-74 (ref. 1) suggested that it, like the related materials TNU-9 (ref. 2) and IM-5 (ref. 3), has a multidimensional 10-ring channel system. Such pore systems are ideal for many petrochemical applications, and indeed SSZ-74 has been shown to be a good catalyst for a wide variety of reactions. The elucidation of its framework structure, however, proved to be difficult. Comparable problems were encountered with TNU-9 and IM-5, which were synthesized with related structure-directing agents. Their framework structures, which are the two most complex ones known, both have 24 Si atoms in the asymmetric unit, and were finally solved by combining high-resolution powder diffraction data with information derived from high-resolution electron microscopy images. Therefore, a similar approach, using the powder charge-flipping algorithm to combine the two types of data and molecular modelling to help to locate the structure-directing agent, was applied to SSZ-74. This procedure eventually revealed a most unusual 23-Si-atom framework structure (|(C16H34N2)4|[Si92 4O184(OH)8]) with ordered Si vacancies.