Supramolecular Assembly of Calcium Metal−Organic Frameworks with Structural Transformations

Six new calcium metal−organic frameworks [Ca(BDC)(DMF)(H2O)] (1), [Ca(ABDC)(DMF)] (2), [Ca3(BTC)2(DMF)2(H2O)2]·3H2O (3), [Ca(H2dhtp)(DMF)] (4), [Ca(H2dhtp)(DMF)2] (5), and one modification of [Ca(H2dhtp)2(H2O)2] (6), (DMF = N,N-dimethylformamide; BDC = 1,4-benzenedicarboxylate anion; ABDC = 2-aminobenzene-1,4-dicarboxylate anion; BTC = 1,3,5-benzenetricarboxylate anion; H2dhtp = 2,5-dihydroxyterephthalate anion) were synthesized from calcium ions and aromatic carboxylic acids by solvothermal reactions and microwave-assisted solvothermal reactions. The single crystal structure analysis showed that all complexes display three-dimensional structures containing various inorganic motifs with helical or straight one-dimensional inorganic chains (1−3), pentagonal bipyramidal dimers (4 and 6), or discrete octahedra (5) connected through organic linkers and forming DMF- or water-coordinated neutral frameworks. It is also interesting that compounds 1−5 undergo dissolution/reorganization reactions comprising a break and reformation of the Ca−O bond and leading to destruction/construction structural transformations. Compounds 1−5 were further characterized by thermal gravimetric analysis, powder X-ray diffraction, UV−vis, infrared, and PL spectroscopy.