Guest-induced expanding and shrinking porous modulation based on interdigitated metal–organic frameworks constructed by 4,4′-sulfonyldibenzoate and barium ions

Abstract

A series of barium-4,4′-sulfonyldibenzoate (sdba) coordination polymers, namely, [Ba(μ₂-OH₂)(sdba)(H₂O)₃]·0.5H₂O (1), [Ba(μ₂-OH₂)(sdba)(H₂O)₃]·0.5ben·H₂O (2), [Ba(μ₂-OH₂)(sdba)(H₂O)₃]·0.5tolu·H₂O (3), [Ba(μ₂-OH₂)(sdba)(H₂O)₃]·0.5bpy·H₂O (4), [Ba(μ₂-OH₂)(sdba)(H₂O)₃]·0.25bim·H₂O (5), [Ba(μ₂-OH₂)(sdba)(H₂O)₃]·0.5dfb·0.25H₂O (6) and [Ba(μ₂-OH₂)(sdba)(H₂O)₃]·3.5H₂O (7) (ben = benzene, tolu = toluene, bpy = 2,2′-bipyridine, bim = 1,4-bis(imidazol-1-yl)butane, dfb = 1,3-difluoro-benzene (a fragment of fluconazole)), have been hydrothermally synthesized and characterized by single crystal X-ray diffraction, powder X-ray diffraction, elemental analysis, IR spectra, and TG analyses. Compounds 1–7 are built upon similar sidearm-containing 2D bilayer motifs, and the adjacent layers are stacked in a mutual interdigitation, such that channels are created. The channels form a hydrogen-bonded interior for guest molecules. In practice, compounds 1 and 7 contain different quantities of free water molecules as guests in the channels, whereas compounds 2–6 contain ben, tolu, bpy, bim and dfb molecules as well as free water molecules in their channels, respectively. The different interlayer distances and free void spaces of 1–7 indicate the effect of guest-induced expanding and shrinking porous modulation, and give a clue to the dynamic arrangement in this system. This indicates the obtained compounds (1–7) are categorized as a member of a new generation of compounds tending towards functional porous coordination polymers. In addition, the photoluminescent properties for all the compounds (1–7) were investigated in detail.