| 초록 |
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 CS 2 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 CS 2 the short diagonal of the rhombic channel expanded by 0.91 A and the maximum spherical void diameter increases to 8.0 A from 7.6 A 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 o -28.2 o , 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 A from 7.6 A upon intercalation of tetrahydrothiophene or thiomorpholine, and to 6.0 A 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. |
