Composite microporous compounds (MIL-n) - II. Hydrothermal synthesis and ab initio resolution by X-ray powder diffraction of MIL-5: A vanadodiphosphonate with a three-dimensional neutral framework

摘要

Moderate heating (473 K) under hydrothermal conditions of a mixture of NH4VO3, ethylenediphosphonic acid, and water in the molar ratio 1:0.57:500 leads to the synthesis of a light blue powder compound formulated (H2O)[V2O2(OH) {O3P(CH2)(2) PO3}] (labeled MIL-5). Its structure was solved ab initio from X-ray powder diffraction data and its symmetry is monoclinic (P2(1)/m (No. 11)) with lattice parameters a 7.903(1) Angstrom, b = 9.355(1) Angstrom, c = 7.485(1) Angstrom, beta = 118.25(1)degrees, V = 487.42(1) Angstrom(3), and Z = 2. The compounds neutral three-dimensional framework is built up from dimeric units of face-shared VO5(OH) octahedra linked by tetrahedral diphosphonic groups. The water molecules are inserted in the cavities of the structure. (C) 1998 Academic Press. [References: 25]