Nets with channels of unlimited diameter

Smith, J. V.; Dytrych, William J.

doi:10.1038/309607a0

Cited by 100 publications

(34 citation statements)

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“…1 by the insertion of one or more crankshaft chains between adjacent trigonal columns along y, in the same way as nets 81(1) [VPI-5 (Davis, Saldarriaga, Montes, Garces & Crowder, 1988)] and 81(2) were derived from structure types 82a (Bennett & Smith, 1985) and AFI (Bennett, Cohen, Flanigen, Pluth & Smith, 1983) respectively by Smith & Dytrych (1984). Furthermore, the symmetry relation between neighbouring trigonal columns along x provides further possibilities for the derivation of new nets.…”

Section: Enumerating Some Subgroupsmentioning

confidence: 99%

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Towards a general description of hexagonal three-dimensional framework structures: the lateral connection of trigonal columns (LCTC) group

Andries¹

1990

Acta Cryst Sect A

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Hexagonal three-dimensional framework structures are constructed from trigonal columns. When two 0108-7673/90/100855-14503.00 types of trigonal column are distinguished, all hexagonal 3D framework structures known to date can be classified in the lateral connection of trigonal columns (LCTC) group. Also, orthorhombic 3D nets © 1990 International Union of Crystallography 856 THE LCTC GROUP can be constructed from trigonal columns and a number of such hypothetical nets related to the hexagonal 81(i) series of Smith & Dytrych [Nature (London) (1984), 309, 607-608] are enumerated. A systematic investigation of the several ways by which neighbouring trigonal columns can be linked and symmetry related gives rise to a large number of subgroups in the present LCTC group. A general designation for LCTC structures by means of a composite code is proposed.

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Section: Enumerating Some Subgroupsmentioning

confidence: 99%

“…WEN (Wenk, 1973; see below), VPI-5, net 81(2) (Smith & Dytrych, 1984) (Gerke & Gies, 1984;see below). In this case, the trigonal columns are directly connected.…”

Section: B Bmentioning

confidence: 99%

Towards a general description of hexagonal three-dimensional framework structures: the lateral connection of trigonal columns (LCTC) group

Andries¹

1990

Acta Cryst Sect A

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“…In the absence of octahedral Al, this framework is net 39(1) originally proposed by Smith and Dytrych.19 If the bonded water is removed from the structure of VPI-5, then net 81(1) (now renumbered to net 52012) is obtained and was also proposed by Smith and Dytrych. 19 The existence of A1P04-H2 and VPI-5 suggests that a material with the topology illustrated in Fig. l(c) can be synthesized.…”

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confidence: 99%

Aluminophosphate molecular sieves comprised of hydrated triple crankshaft chains

Li¹,

Davis²,

Higgins³

et al. 1993

J. Chem. Soc., Chem. Commun.

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We report the first synthesis of pure aluminophosphate hydrate H2 (AIP04-H2) and its structure; AIP04-H2 is constructed exclusively from a hydrated chain building unit that also builds the 18-ring VPI-5 structure and has one-dimensional channels circumscribed by highly elliptical rings consisting of ten oxygen atoms, implications from the existence of this building unit for the synthesis of novel aluminophosphate molecular sieves and for the synthesis of aluminosilicate and silicate analogues of AlP04-H2 and VPI-5 are discussed.In 1961, d'Yvoire1 reported the synthesis of the aluminophosphate hydrates H1, H2, H3 and H4 (denoted here with prefix AlP04-). Only the structure of AlP04-H3 has been determined. Using single crystal X-ray diffraction methods, Pluth and Smith2 found A1 in A1PO4-H3 coordinated to either four or six oxygen atoms. More recently, Keller et. aZ.3 showed that A1P04-H3 reversibly dehydrates to A1P04-C which contains only four-coordinated aluminium. The increased coordination of aluminum above four in A1PO4-H3 is due to bound water molecules. In 1982, workers at Union Carbide reported the synthesis of aluminophosphate molecular sieves with pore diameters below 8 A.4 Hundreds of aluminophosphates and heteroatom substituted aluminophosphates with approximately 27 topologies are now known. Most notably, the aluminophosphate VPI-5 contains the largest pore of all the tetrahedral frameworks.5Jj In addition, the aluminophosphates A1Po4-87 and JDF-208 (interrupted framework) and the gallophosphate cloverite9 (interrupted framework) contain rings larger than those observed in non-phosphate-based molecular sieves, e.g., zeolites. Thus, there is great current interest in synthesizing silica-based molecular sieves, with a pore size similar to VPI-5.Early on, we recognized some similarities in the X-ray diffraction patterns of VPI-5 and A1P04-H1 .lo Since then, we have attempted to repeat d'Yvoire's work. In the course of this investigation, pure A1P04-H2 was synthesized for the first time (d'Yvoire1 and others11 have synthesized the hydrate A1P04-H2 in the presence of one or more other hydrated aluminophosphate phases, e.g. , A1P04-H1, A1P04-H3, A1PO4-H4, variscite and metavariscite). Highly crystalline A1P04-H2 is synthesized at hydrothermal conditions from an aluminophosphate gel containing di-n-pentylamine (R) . A phosphoric acid solution is added slowly to an alumina (Catapal B) slurry to form an aluminophosphate gel. The gel is aged for 8 h before addition of the amine. The molar composition of the final mixture is R : A1203 : P 2 0 5 : 50 H 2 0 . The crystallization is carried out in Teflon-lined autoclaves at 393 K for one to two days. The amine does not function as a structure-directing agent since it is not present in the A1P04-H2 material after synthesis. The successful synthesis of pure A1P04-H2 enabled structure determination. Detailed discussions of the X-ray structure determination and refinement procedures will be given elsewhere.12 A1PO4-H2 is orthorhombic with a = 16.184(5), b = 9.914(3), ...

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“…[4][5][6][7] The reason for this is the desire to perform catalysis/ adsorption on molecules > 8 Å in size.The first molecular sieve with extra-large pores was VPI-5 that is an aluminophosphate material with 18-ring pores. 8 Subsequently, other phosphate-based extra-large pore materials have been reported, e.g.…”

mentioning

confidence: 99%

“…[4][5][6][7] The reason for this is the desire to perform catalysis/ adsorption on molecules > 8 Å in size.…”

mentioning

confidence: 99%

CIT-5: a high-silica zeolite with 14-ring pores

Yoshikawa¹,

Tsuji²,

Davis³

et al. 1997

Chem. Commun.

150

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The synthesis and structure of a new zeolite, CIT-5 (California Institute of Technology Number Five), is described, which possesses one-dimensional pores comprised of 14 T-atoms (tetrahedrally coordinated silicon or aluminium atoms).Zeolites with pores comprised of larger than 12 T-atoms (extralarge pores) are much in demand 1-4 and have been so for many years. [4][5][6][7] The reason for this is the desire to perform catalysis/ adsorption on molecules > 8 Å in size.The first molecular sieve with extra-large pores was VPI-5 that is an aluminophosphate material with 18-ring pores. 8 Subsequently, other phosphate-based extra-large pore materials have been reported, e.g. cloverite. 2 All of the phosphate-based molecular sieves lack the desired properties of combined high acidity and thermal/hydrothermal stability and thus limit the practical potential. Recently, the first extra-large pore zeolite, UTD-1, was reported and shown to possess good acidity and thermal/hydrothermal stability. 9,10 Additionally, there have been numerous disclosures of ordered, aluminosilicate mesoporous materials with pore sizes of 20-100 Å. 11,12 Because the inorganic portions of the mesoporous materials are not crystalline, they lack the acidity and thermal/hydrothermal stability of high-silica zeolites. 13 Here, we report a new extra-large pore zeolite denoted CIT-5. CIT-5 is synthesized under hydrothermal conditions. A reaction mixture of composition 0.2 ROH : 0.1 LiOH : 0.02 Al 2 O 3 : 1 SiO 2 : 40 H 2 O is heated to 175 °C at autogenous pressure for ca. 12 d in order to produce CIT-5. In the absence of aluminium, pure-silica CIT-5 can be prepared in 5 d. The organic structuredirecting agent (SDA), R, is N(16)-methylsparteinium I and is prepared as previously reported. 14 In the absence of lithium, I can form pure-silica or borosilicate SSZ-24. 13,14 Thus, the key to the successful preparation of CIT-5 is both the SDA I and the inclusion of lithium. Further synthetic details are forthcoming. 15 Indexation 16 of the synchrotron powder X-ray diffraction (SPXRD) data from the pure-silica sample of CIT-5 revealed the presence of a small amount of an impurity phase together with the predominant CIT-5 phase. The CIT-5 material indexed in the orthorhombic crystal class with refined lattice constants a = 13.694(2), b = 5.0213(5), and c = 25.4970(3) Å (U = 1753.2 Å 3 ). The lattice constants for the impurity hexagonal phase were found to be a = 13.63 and c = 8.30 Å. The unit cell parameters and scanning electron micrographs helpd to identify the impurity phase as SSZ-24 (International Zeolite Association Code AFI). 17 Systematic absences for the orthorhombic CIT-5 phase indicate body-centering consistent with six possible space groups.The starting model for Rietveld refinement of CIT-5 was obtained by an iterative process of model building, distanceleast squares (DLS) 18 refinement of the atomic positions for the model, and comparison of the simulated powder X-ray pattern (CERIUS 19 ) to the experimental pattern. The model with the closest ma...

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Nets with channels of unlimited diameter

Cited by 100 publications

References 16 publications

Towards a general description of hexagonal three-dimensional framework structures: the lateral connection of trigonal columns (LCTC) group

Towards a general description of hexagonal three-dimensional framework structures: the lateral connection of trigonal columns (LCTC) group

Aluminophosphate molecular sieves comprised of hydrated triple crankshaft chains

CIT-5: a high-silica zeolite with 14-ring pores

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