Hydrothermal synthesis and crystal structure of a new three-dimensional aluminum-organic framework MIL-69 with 2,6-naphthalenedicarboxylate (ndc), Al(OH)(ndc)•H2O

A new three-dimensional aluminum-organic framework, MIL-69 or Al(OH)(O2C-C10H6-CO2)(H2O)-H-., has been hydrothermally synthesized at 210 degrees C for 16 h, by using 2,6-naphthalenedicarboxylic acid as a rigid ligand. The model for the crystal structure of MIL-69 was determined by means of lattice energy minimizations and further refined against the powder XRD data using the Rietveld refinement method. The crystal structure consists of infinite chains of AlO4(OH)(2) octahedra corner-linked through the mu(2)-hydroxyl groups and connected by the 2,6-naphthalenedicarboxylate moieties. It results in the formation of flat channels parallel to the chains of aluminum octahedra, running along the c axis. A water molecule is trapped nearby the center of the tunnels and mainly interacts via hydrogen bonds with the hydroxyl groups and the oxygen atoms of the carboxylates. Although the three-dimensional aluminum-organic framework is stable up to 450 degrees C, the tunnels still remain shrunk upon removal of water molecule, because of the occurrence 7r-n interactions between the naphthalene groups. The MIL-69 phase was characterized by solid state NMR MAS(27)Al, H-1 and C-13{H-1-decoupled}, which is consistent with the crystal structure description. Crystal data. - MIL-69, Al(OH)(O2C-C10H6-CO2)(H2O)-H-.: Mr = 267.11 g mol(-1), monoclinic, space group C2/c (no. 15), a = 24.598(2) angstrom, b = 7.5305(6) angstrom, c = 6.5472(5) angstrom, beta = 106.863(8)degrees, V = 1160.6(2) angstrom(3), Z = 4. (c) 2005 Academie des sciences. Published by Elsevier SAS. All rights reserved.