4.6 Article

Elucidating the Germanium Distribution in ITQ-13 Zeolites by Density Functional Theory**

期刊

CHEMISTRY-A EUROPEAN JOURNAL
卷 28, 期 14, 页码 -

出版社

WILEY-V C H VERLAG GMBH
DOI: 10.1002/chem.202104298

关键词

AIMD simulations; DFT calculations; fluoride anions; NMR spectroscopy; zeolites

资金

  1. Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) [389577027 (FI 1800/5-1)]
  2. North-German Supercomputing Alliance (HLRN) [hbc00030]
  3. FCT [PD/BD/142849/2018, PD/00065/2013]
  4. FCT/MEC [UIDB/50011/2020, UIDP/50011/2020, LA/P/0006/2020]
  5. Projekt DEAL
  6. Fundação para a Ciência e a Tecnologia [PD/BD/142849/2018] Funding Source: FCT

向作者/读者索取更多资源

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. The energetically most favourable Ge distributions for Si/Ge ratios between 55 and 6 have been investigated using dispersion-corrected density functional theory calculations, showing Ge atoms are incorporated at specific locations in the cages.
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 . 5(6)] 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 . 5(6)] cages, in accordance with F-19 NMR spectroscopy. Two Ge atoms at adjacent corners of [4 . 5(6)] 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 F-19 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 . 5(6)] cages.

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