Framework deformation of the microporous vanadium benzenedicarboxylate MIL-47 upon absorption of organosulfur molecules

Deformation of the microporous MIL-47 framework VO(bdc), bdc = 1,4-benzenedicarboxylate, upon absorption of carbon disulfide, tetrahydrothiophene, thiomorpholine and thioxane is investigated by single crystal X-ray diffraction. Intercalation of CS2 significantly expands the channel opening by a breathing deformation mode of the framework characterized solely by a cooperative translation of the octahedral chains, in contrast to intercalation of many other molecules that usually cause contraction of the channel opening. Upon loading of CS2 the short diagonal of the rhombic channel expanded by 0.91 angstrom and the maximum spherical void diameter increases to 8.0 angstrom from 7.6 angstrom of VO(bdc) with empty channels. Loading of the three cyclic organosulfur molecules all results in a strong twisting deformation of the framework featured by cooperative rotation of the octahedral chains by 21.3 degrees-28.2 degrees, bending of the bdc ligand and lowering of the space group symmetry from Pnma to P2(1)2(1)2(1). The maximum spherical void diameter of the framework decreases to 6.8 angstrom from 7.6 angstrom upon intercalation of tetrahydrothiophene or thiomorpholine, and to 6.0 angstrom upon intercalation of thioxane. Intercalation of thioxane leads to the highest degree of twisting known for the VO(bdc) framework combined with a substantial breathing contraction of the channel. The host-guest interactions are predominantly van der Waals in nature and the framework deformations are presumably driven by maximizing the van der Waals contacts. (C) 2015 Elsevier Inc. All rights reserved.