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Title: | Elucidating the Germanium Distribution in ITQ-13 Zeolites by Density Functional Theory |
Author: | Fischer, Michael Bornes, Carlos Mafra, Luís Rocha, João |
Issue Date: | 7-Mar-2022 |
Publisher: | Wiley-Blackwell |
Abstract: | ITQ-13 is a medium-pore zeolite that can be prepared in all-silica form and as silicogermanate with Si/Ge ratios as low as 3. Usually synthesised in the presence of fluoride, ITQ-13 is among the very few systems containing fluoride anions in two distinct cage types, cube-like d4r units and [4 ⋅ 56 ] cages. Here, dispersion-corrected density functional theory (DFT) calculations are used to investigate the energetically most favourable Ge distributions for Si/Ge ratios between 55 and 6. The calculations show Ge atoms are incorporated at both the corners of d4r cages and at the basal plane of the [4 ⋅ 56 ] cages, in accordance with 19 F NMR spectroscopy. Two Ge atoms at adjacent corners of [4 ⋅ 56 ] cages are stable at the highest Ge content considered (Si/Ge=6). Such a local environment has not yet been considered in the experimental literature. A calculation of the corresponding 19 F NMR resonance points to overlap with other resonances, which might preclude its clear identification. Additional calculations investigate the variation of the dynamic behaviour of the fluoride anions as a function of the local environment as well as the selective defluorination of the [4 ⋅ 56 ] cages. |
Peer review: | yes |
URI: | http://hdl.handle.net/10773/35813 |
DOI: | 10.1002/chem.202104298 |
ISSN: | 0947-6539 |
Appears in Collections: | CICECO - Artigos DQ - Artigos |
Files in This Item:
File | Description | Size | Format | |
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Chemistry A European J - 2022 - Fischer - Elucidating the Germanium Distribution in ITQ%E2%80%9013 Zeolites by Density Functional.pdf | 4.57 MB | Adobe PDF | View/Open |
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