Hydrothermal crystal growth and Vernier structures of the metal benzenedicarboxylates MIL-47 and MIL-53 containing guest molecules of benzenecarboxylic acid

The nanoporous frameworks VO(bdc), MIL-47, and M(OH)(bdc), MIL-53; bdc=1,4-benzenedicarboxylate, can absorb various guest species in their channels. As synthesized, the channels are filled with H(2)bdc molecules that have been reported to be disordered, except for [In(OH)bdc](H(2)bdc)(3/4), 1, which has a inorganic-organic hybrid Vernier structure with the H(2)bdc molecules forming an ordered sublattice. Based on X-ray data from large single crystals grown by hydrothermal techniques, similar Vernier structures have been found for MIL-47, [VO(bdc)](H(2)bdc)(5/7), 2, MIL-53Al, [Al(OH)(bdc)](H(2)bdc)(11/16), 3 and MIL-53Ga, [Ga(OH)(bdc)](H(2)bdc)(12/17), 4. The Vernier structures of 2-4 at room temperature were determined based on superstructure unit cells that index both host and guest sublattices: 2, space group P2(1), a=23.903(2), b=17.191(2), c=25.722(2) angstrom, beta=105.914(8)degrees; 3, P2(1)/n, a=105.224(4), b=12.2441(5), c=17.0143(6) angstrom, beta=89.99(1)degrees; 4, P2(1), a=114.562(5), b=12.1503(5), c=17.4275(7) angstrom, beta=89.99(1)degrees. The number of guest H(2)bdc molecules per framework metal ion is determined by the ratio of the repeat distances of the two sublattices which depends on the size of the metal ion in the octahedral chain. The octahedral chains are parallel to [201] in 2, and to [100] in 3 and 4. Remarkably, all atoms in 3 and 4 show significant sinusoidal modulations transverse to the chain axis. (C) 2015 Elsevier Inc. All rights reserved.