Complex zeolite structure solved by combining powder diffraction and electron microscopy

Many industrially important materials, ranging from ceramics to catalysts to pharmaceuticals, are polycrystalline and cannot be grown as single crystals. This means that non-conventional methods of structure analysis must be applied to obtain the structural information that is fundamental to the understanding of the properties of these materials. Electron microscopy might appear to be a natural approach, but only relatively simple structures have been solved by this route. Powder diffraction is another obvious option, but the overlap of reflections with similar diffraction angles causes an ambiguity in the relative intensities of those reflections. Various ways of overcoming or circumventing this problem have been developed(1,2), and several of these involve incorporating chemical information into the structure determination process(3-7). For complex zeolite structures, the FOCUS algorithm(8,9) has proved to be effective. Because it operates in both real and reciprocal space, phase information obtained from high-resolution transmission electron microscopy images can be incorporated directly into this algorithm in a simple way. Here we show that by doing so, the complexity limit can be extended much further. The power of this approach has been demonstrated with the solution of the structure of the zeolite TNU-9 (\H-9.3\[ Al9.3Si182.7O384]; ref. 10) with 24 topologically distinct ( Si, Al) atoms and 52 such O atoms. For comparison, ITQ-22 ( ref. 11), the most complex zeolite known to date, has 16 topologically distinct (Si, Ge) atoms.</p

Structure and catalytic properties of the most complex intergrown zeolite ITQ-39 determined by electron crystallography

[EN] Porous materials such as zeolites contain well-defined pores in molecular dimensions and have important industrial applications in catalysis, sorption and separation. Aluminosilicates with intersecting 10- and 12-ring channels are particularly interesting as selective catalysts. Many porous materials, especially zeolites, form only nanosized powders and some are intergrowths of different structures, making structure determination very challenging. Here, we report the atomic structures of an aluminosilicate zeolite family, ITQ-39, solved from nanocrystals only a few unit cells in size by electron crystallography. ITQ-39 is an intergrowth of three different polymorphs, built from the same layer but with different stacking sequences. ITQ-39 contains stacking faults and twinning with nano-sized domains, being the most complex zeolite ever solved. The unique structure of ITQ-39, with a three-dimensional intersecting pairwise 12-ring and 10-ring pore system, makes it a promising catalyst for converting naphtha into diesel fuel, a process of emerging interest for the petrochemical industry.The authors acknowledge financial support from the Spanish MICINN, Consolider Ingenio 2010-Multicat, Generalitat Valenciana through the PROMETEO programme, the Swedish Research Council (VR), the Swedish Governmental Agency for Innovation Systems (VINNOVA) and the Goran Gustafsson Foundation for Natural Scientific and Medical Research. M. Moliner also acknowledges support from the 'Subprograma Ramon y Cajal' (contract RYC-2011-08972). Wei Wan is supported by postdoctoral grants from the Carl-Trygger Foundation. The EM facility was supported by the Knut and Alice Wallenberg Foundation. 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