Ab initio structure determination of novel small-pore metal-silicates: knots-and-crosses structures
authors Ferreira, A; Lin, Z; Soares, MR; Rocha, J
nationality International
journal INORGANICA CHIMICA ACTA
author keywords silicon; solid-state structures; tin; zirconium; hafnium; zeolites
keywords CRYSTALLINE INORGANIC SOLIDS; MOLECULAR-SIEVES; FRAMEWORK; STANNOSILICATES; EXCHANGE; OXIDES
abstract Sodium chloride stannosilicate AV-13 (Na2.26SnSi3O9Cl0.26.xH(2)O) and zirconium and hafnium analogues of this material have been prepared and their structures solved from powder X-ray diffraction data using direct methods, and Na-23, Si-29 and Sn-119 solid-state NMR. AV-13 materials are small-pore solids, probably more adequately described as tunnel structures. The AV-13 framework consists of corner-sharing MO6 (M = Sn, Zr, Rf) octahedra and SiO4 tetrahedra. The latter form six-membered [Si6O18](12-) rings, which are interconnected by MO6 octahedra. The structure is better understood by considering a three-dimensional knots- and-crosses lattice. In a given layer, successive distorted-cube M-8 cages contain [Na6-x(H2O)](H2O,Cl-) octahedra (knots) and cyclohexasilicate (crosses) units. While the former are extra-framework species, the six-membered rings are, of course, part of the framework. The cages are accessed via seven-membered [M3Si4O27](26-) windows, with free aperture ca. 2.3 x 3.2 Angstrom, one per each pseudo-cube face. Pilling up layers generates the structure, with knots-and-crosses alternating. The non-framework five-coordinated Na cations are disordered. (C) 2003 Elsevier Science B.V. All rights reserved.
publisher ELSEVIER SCIENCE SA
issn 0020-1693
year published 2003
volume 356
beginning page 19
ending page 26
digital object identifier (doi) 10.1016/S0020-1693(03)00332-3
web of science category Chemistry, Inorganic & Nuclear
subject category Chemistry
unique article identifier WOS:000187229700004
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