The synthesis and characterization of microporous open-framework transition metal silicates and metal-organic frameworks

The goal of this work is to synthesize microporous materials using hydrothermal techniques. The products were characterized by single crystal and powder X-ray diffraction structural analyses and other characterization methods including thermogravimetric analysis, infrared spectroscopy, diffusive reflectance UV-Vis spectroscopy, scanning electron microscopy, elemental analysis, N2 adsorption, and magnetic susceptibility measurements.; Synthesis and characterization investigations in this work were conducted in two distinct areas: inorganic and inorganic-organic hybrid framework compounds.; Exploratory studies were carried out mainly on transition metal silicates using alkali metals and organics as templates for framework construction. During the studies, a new open-framework vanadium silicate, Na3V(Si 4O11)·H2O was successfully synthesized hydrothermally. Investigation into the hydrothermal synthesis of alkali metal uranium silicates has led to the discovery of seven new compounds: Na 2(UO2)(Si8O22)·2H2O, Rb4(UO2)2(Si8O20), NaRb(UO 2)(Si2O6)·H2O, Rb2(UO 2)(Si2O6)·H2O, A2(UO 2)(Si2O6)·0.5H2O (A = Rb/Cs), Cs2(UO2)(Si6O14), and K6 (UO2)3(Si8O22). These structures are based on interconnected SiO4 tetrahedra and UO6 tetragonal bipyramids. The silicate topologies vary from tetrahedral 4-ring, octamer, double chains, to single layers while all UO6 tetragonal bipyramids are isolated and contain the linear (O=U=O)2+ ion. The nonframework space is filled by alkali cations.; The compound [(CH3)4N][(C5H5)N](UO 2F2)2(Si9O19), which was synthesized in a non-aqueous HF/pyridine/TMAOH solvent system, is to our knowledge, the first organically templated open-framework uranium fluorosilicate. The framework is characterized by silicate double layers with a high density of 5-ring channels and single chains of fluorouranate pentagonal bipyramids. The same silicate double layer is found in the structure of the zeolite ferrierite. Organic cations are occluded inside the channels.; In the second area of inorganic-organic hybrid frameworks, microporous structures composed of Al-oxo groups bridged by dicarboxylate ligands were explored. Single crystals of a novel microporous open-framework Al(OH)(C 8H4O4)·0.7(C8H6O 4) was hydrothermally synthesized. Al(OH)(C8H4O 4)·(H2O), Al(OH)(C8H4O 4)·(C5H5N) and Al(OH)(C8H 4O4)·0.8(C5H5N) were also prepared via calcinations of Al(OH)(C8H4O4)·0.7(C 8H6O4) followed by water and pyridine sorption, respectively. The four structures exhibit the same framework topology. The three dimensional frameworks are constructed from Al-O-Al chains that are cross-linked by 1,4-benzene dicarboxylate (BDC) anions forming large diamond shaped one-dimensional channels. Additional disordered H2BDC, water, and pyridine molecules reside inside the channels of the corresponding compounds. A room temperature structural transformation was observed between Al(OH)(C 8H4O4)·(C5H5N) and Al(OH)(C8H4O4)·0.8(C5H 5N). The transformation was characterized to be fully reversible and induced by the pyridine concentration.