Multidimensional Disorder in Zeolite IM-18 Revealed by Combining Transmission Electron Microscopy and X-ray Powder Diffraction Analyses

Abstract

A new medium-pore germanosilicate, denoted IM-18, with a three-dimensional 8 × 8 × 10-ring channel system, has been prepared hydrothermally using 4-dimethylaminopyridine as an organic structure-directing agent (OSDA). Due to the presence of stacking disorder, the structure elucidation of IM-18 was challenging, and a combination of different techniques, including electron diffraction, high-resolution transmission electron microscopy (HRTEM), and Rietveld refinement using synchrotron powder diffraction data, was necessary to elucidate the details of the structure and to understand the nature of the disorder. Rotation electron diffraction data were used to determine the average structure of IM-18, HRTEM images to characterize the stacking disorder, and Rietveld refinement to locate the Ge in the framework and the OSDA occluded in the channels.

Elucidation of correlated disorder in zeolite IM-18

“…1) of the polycrystalline sample which contains both the sharp and broad diffraction peaks is similar to that of reported samples of IM-18 ( Fig. S2) (Lorgouilloux et al, 2011;Cichocka et al, 2018). There are two obvious broad peaks in the PXRD pattern of IM-18, which approximately range from 8.0 to 11.5 and 24.5 to 28.0 .…”

“…The main body of the product reacted for 21 days was still composed of small grains, but a certain quantity of the single crystals could be picked for the SXRD test. The reaction conditions are different from the reported synthesis condition, which was conducted with the composition of 0.8SiO 2 : 0.2GeO 2 :0.75D-MAP : 0.5HF : 3H 2 O reacted at 170 C for 14 days (Lorgouilloux et al, 2011;Cichocka et al, 2018).…”

“…The zeolite IM-18 was reported to be synthesized with 4dimethylaminopyridine (DMAP) as the organic structuredirecting agent (OSDA) (Lorgouilloux et al, 2011). Recently, X. Zou and J. L. Paillaud reported excellent work to elucidate its structure by combining rotation electron diffraction (RED) and Rietveld refinement of PXRD (Cichocka et al, 2018). The space group Imma of the average structure was determined from the RED data while the space group P2 1 /m was used to refine the structure to fit the PXRD data due to the influence of disorder.…”

Transmission electron microscopy as an important tool for characterization of zeolite structures

“…HRTEM is especially useful for studying zeolite crystals that contain disorders such as stacking faults, twinning and intergrowth. 18,50 ED is an important technique for phase identification and determination of crystal orientation, for crystals down to a few nanometers in size. Unit cell and space group information, as well as intensities of reflections can also be obtained from ED patterns, which can be used for structure solution of novel zeolites.…”

New zeolite-like RUB-5 and its related hydrous layer silicate RUB-6 structurally characterized by electron microscopy

“…Regardless of the acquisition method used, dedicated programs such as eADT (former ADT3D), PETS, RED and EDT-PROCESS (Kolb et al, 2019;Palatinus, 2011;Wan et al, 2013;Oleynikov, 2011;Gemmi & Oleynikov, 2013) are employed to reconstruct the 3D reciprocal lattice, which allows the determination of cell parameters, the space group and furthermore the extraction of intensities suitable for structure solution by direct methods, charge flipping or simulated annealing in analogy to X-ray diffraction experiments. The ability to also reconstruct the raw diffraction pattern into 3D data simplifies the interpretation of disorder, phase mixtures and twinning (Kolb et al, 2011(Kolb et al, , 2019Su et al, 2014;Cichocka et al, 2018;Mayorga-Martinez et al, 2018).…”