Synthesis, Characterization, and Framework Heteroatom Localization in ITQ-21
- 23 September 2004
- journal article
- Published by American Chemical Society (ACS) in Journal of the American Chemical Society
- Vol. 126 (41) , 13414-13423
- https://doi.org/10.1021/ja047990z
Abstract
ITQ-21 has been synthesized in a wide range of compositions. By rationally modifying the synthesis variables and zeolite composition, it is possible to fine-tune the crystallite size from nanocrystals (19F MAS NMR, Ge and Si have been localized among the different crystallographic positions, and it is shown that Ge preferentially occupies T1 positions at the D4R cages, avoiding formation of Ge−O−Ge pairs. However, at high Ge loadings (Si/Ge = 1.7), a new 19F MAS NMR signal at −14 ppm has been observed and assigned to the presence of Ge−O−Ge in Ge-rich D4R cages. Energetic configurations obtained by theoretical calculations fully agree with experimental observations, with the following increasing order in energy for Ge substitution: T1 < T2 < Ge−O−Ge in T1 < T3.Keywords
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