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Synthesis and structures of new silicogermanates
Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
2004 (English)In: Studies in Surface Science and Catalysis, ISSN 0167-2991, Vol. 154, no 1, 739-745 p.Article in journal (Refereed) Published
Abstract [en]

Three new micro-porous silicogermanates, (NH4)F[(Ge3.14Si6.86)O20] (SU-9), (NH4F[(Ge6.78Si3.22)O20] (SU-10) and [(Ge2.40Si9.60)O24] (SU-11) were synthesized under hydrothermal conditions with the presence of structure directing agents and the structures were solved by single crystal X-ray diffraction. SU-9 and SU-10 are built up by the double T4-rings (D4Rs) and they have the zeolite structure types of AST and ASV, respectively. SU-11 is built up by the T12-units and has the zeolite structure type of MFI. In three compounds, both silicon and germanium atoms are tetrahedrally coordinated with oxygen atoms and share the same tetrahedral sites.

Place, publisher, year, edition, pages
Elsevier B.V. , 2004. Vol. 154, no 1, 739-745 p.
Keyword [en]
silicogermanate; AST; ASV; MFI; hydrothermal synthesis
National Category
Environmental Sciences
Identifiers
URN: urn:nbn:se:su:diva-23658DOI: 10.1016/S0167-2991(04)80878-4OAI: oai:DiVA.org:su-23658DiVA: diva2:193886
Note
Part of urn:nbn:se:su:diva-440Available from: 2005-04-05 Created: 2005-04-05 Last updated: 2011-01-31Bibliographically approved
In thesis
1. Novel framework materials: organically templated silicogermanates and hybrid fluorotitanates
Open this publication in new window or tab >>Novel framework materials: organically templated silicogermanates and hybrid fluorotitanates
2005 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Two types of novel framework materials, including six organically templated silicogermanates and five hybrid fluorotitanates, have been synthesized, and their structures have been determined by single crystal X-ray diffraction. Their structures and the interactions between the organic and inorganic species are discussed in some detail.

The frameworks of the six silicogermanates, SU-9, SU-10, SU-11, SU-12, SU-14 and SU-21, are built up from either tetrahedra exclusively, or from mixed polyhedra. SU-9, SU-10 and SU-11 consist only of tetrahedra, and SU-12, SU-14 and SU-21 are built up from mixed polyhedra. In all silicogermanates, Si and Ge share the tetrahedrally coordinated positions, and only Ge occupies the 5- and 6-coordinated positions.

The frameworks of SU-9, SU-10 and SU-11 belong to zeolite frameworks. SU-9 and SU-10 are built up from the same periodic building units (PBUs) that are formed by 4/4-4 units, and they adopt the known zeolite framework types AST and ASV, respectively. SU-11 is built up from 5-1 units and adopts the known zeolite framework type MFI. This is the first time that the frameworks of AST, ASV and MFI have been prepared in silicogermanate form.

The 3-D frameworks of SU-12 and SU-14 contain (Ge,Si)7 composite building units that form one-dimensional 24-ring channels along the c axis. Their structures contain intersecting channels. SU-12 contains 8-, 10- 12- and 24-ring channels; while SU-14 has 9-, 10-, 12- and 24-ring channels. SU-21 is a two-dimensional framework structure containing 10-ring channels. It is the first silicogermanate with the template covalently bonded to Ge.

All silicogermanates were synthesized by using organic amines as templates. The templates play a very important role in directing the structure of the inorganic framework.

The obtained five hybrid fluorotitanates are SUF-1, SUF-2, SUF-3, SUF-4 and SUF-5. Their hybrid frameworks are built up from fluorotitanate anions, N-containing cations and crystal water/oxonium cations. Zero-dimensional fluorotitanate clusters are normally obtained when cyclic organic amines such as 1,4-diazabicyclo[2,2,2]octane (DABCO) and piperazine are used. Increasing the pH value of the starting solutions led to more condensed fluorotitanate anions, from isolated octahedra to pairs and eventually chains of octahedra. The formation of the hybrid frameworks of fluorotitanates is strongly dependent on hydrogen bonds between the fluorotitanate anions, N-containing organic cations and water molecules/oxonium ions.

Place, publisher, year, edition, pages
Stockholm: Institutionen för fysikalisk kemi, oorganisk kemi och strukturkemi, 2005. 88 p.
Keyword
framework materials, silicogermanates, hybrid fluorotitananates
National Category
Chemical Sciences
Identifiers
urn:nbn:se:su:diva-440 (URN)91-7155-048-8 (ISBN)
Public defence
2005-05-02, Magnélisalen, Kemiska övningslaboratoriet, Svante Arrhenius väg 12 A, Stockholm, 10:00
Opponent
Supervisors
Available from: 2005-04-05 Created: 2005-04-05Bibliographically approved

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