Structure determination of zeolites by electron crystallography

Abstract

Many zeolite structures have remained unsolved for a long time because of their structural complexity, the size of the crystallites or the presence of defects or impurities. By combining electron microscopy and X-ray powder diffraction data, some of them have been solved (e.g. the high-silica zeolite IM-5, which was first reported in 1998 [1] and recently solved using a charge-flipping structure solution algorithm [2]), while for other zeolites, good X-ray powder diffraction data are hard to obtain (e.g. polymorph A or B of zeolite Beta). Here we demonstrate a complete structure determination of IM-5 (one of the most complicated zeolited) and polymorph B of zeolite Beta [3] using electron crystallography alone. This shows the power and advantage of structure determination by electron microscopy compared with the X-ray diffraction techniques. The method is general and can be applied to both zeolites and other materials, where the crystals are too small or the structure too complicated to be solved from X-ray powder diffraction data alone [4]. It is particularly useful for structures containing defects.