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

• Loading of CS2 leads to the most open VO(bdc) framework as a result of cooperative translation of the octahedral chains.
• Intercalation of thioxane causes the highest degree of twisting deformation among all known [VO(bdc)]
• guest systems.
• The space group symmetry changes from Pnma to P212121 upon absorption of tetrahydrothiophene, thiomorpholine or thioxane.

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 Å and the maximum spherical void diameter increases to 8.0 Å from 7.6 Å 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°–28.2°, bending of the bdc ligand and lowering of the space group symmetry from Pnma to P212121. The maximum spherical void diameter of the framework decreases to 6.8 Å from 7.6 Å upon intercalation of tetrahydrothiophene or thiomorpholine, and to 6.0 Å 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.

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