Liqiu Tang

A zeolite family with chiral and achiral structures built from the same building layer

Porosity and chirality are two of the most important properties for materials in the chemical and pharmaceutical industry. Inorganic microporous materials such as zeolites have been widely used in ion-exchange, selective sorption/separation and catalytic processes. The pore size and shape in zeolites play important roles for specific applications. Chiral inorganic microporous materials are particularly desirable with respect to their possible use in enantioselective sorption, separation and catalysis. At present, among the 179 zeolite framework types reported, only three exhibit chiral frameworks. Synthesizing enantiopure, porous tetrahedral framework structures represents a great challenge for chemists. Here, we report the silicogermanates SU-32 (polymorph A), SU-15 (polymorph B) (SU, Stockholm University) and a hypothetical polymorph C, all built by different stacking of a novel building layer. Whereas polymorphs B and C are achiral, each crystal of polymorph A exhibits only one hand and has an intrinsically chiral zeolite structure. SU-15 and SU-32 are thermally stable on calcination.

Synthesis and structures of new silicogermanates

Abstract Three new micro-porous silicogermanates, ‖(NH 4 )F‖[(Ge 3.14 Si 6.86 )O 20 ] (SU-9), ‖(NH 4 F‖[(Ge 6.78 Si 3.22 )O 20 ] (SU-10) and [(Ge 2.40 Si 9.60 )O 24 ] (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.

Open-framework germanates — A study of nets and tilings

Abstract A series of open-framework germanates, alumino- and silico-germanates were synthesized (denoted as SU-n). Most of them were built from a few types of inorganic clusters containing a well-defined number of polyhedra: Ge 3 O 9 (4=1), Ge 4 O 16 (D4R) and larger clusters including 7, 9 and 10 Ge atoms (named Ge 7 , Ge 9 , Ge 10 clusters, respectively). Different arrangements and combinations of these clusters resulted in different open-framework structures including several novel zeolite frameworks. Here, we examine the different underlying nets and tilings observed in germanate-based compounds synthesized by our group and others.

Design of three-dimensional open-framework structures from inorganic clusters

Abstract A series of open-framework germanates and silicogermanates were synthesized (denoted as SU-n) hydro-/solvo-thermally. Their structures were built from a single or two types of inorganic clusters containing a number of well-defined Ge-O coordination polyhedra. Different arrangements and combinations of these clusters resulted in different open-framework structures including some germanate/silicogermanates with extra-large pores (16–24 rings). Herein we present our recently discovered crystalline structures of SU-3, SU-8, SU-12, SU-44, SU-M and SU-MB. SU-M and SU-MB contain 30-ring channels and pores extending to the mesoporous range (> 20A).

Crystal structure of dipiperazine decafluorooxodititanate dihydrate, (C4H12N2)2[Ti2F10O)]·2H2O

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.

Crystal structure of 1,4-diazabicyclo[2.2.2]octane hexafluorotitanium hydrate, (C6H14N2)[TiF6] · H2O

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.

Crystal structure of dipiperazine decafluorodititanate dihydrate, (C4H12N2)2(Ti2F10] · 2H2O

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.