Syntheses, Structures and Properties of Metal-organic Frameworks Based on Dicarboxylate Ligands
|School||East China Normal University|
|Keywords||Metal-organic framework dicarboxylate ligand crystal structure thermal stability fluorescence adsorption properties|
Metal-organic frameworks have been given much attention from both scientific and commercial aspects because of their potential application in gas storage and separation, catalytic reaction etc owing to their fansinating structures, regularity of the pore shape and size accompanied with the functionality. The organic ligands containing two ore more carboxylate groups offer great potentials for fine control over coordination architectures due to their various coordination modes. In this thesis, dicarboxylate ligand with amide functional group is employed as bridging ligand to assemble with transition metal ions and afforded ten new metal-organic frameworks, including one dimentional, two dimentional and three dimentional architectures. The synthesis, crystal structure, IR, TGA of the ten complexes will be documented in detail. The fluorescence and gas adsorption properties of some complexes have also been studied. The main results can be summarized in four parts:1. Synthesis of ligand 4,4’-[benzenetriyltris(canbonlimino)](benzoate) acid (H2CBDB):It was obtained from organic reaction using terephthalic acid and 4-aminobenzoic acid and was characterized by IR spectrum,1H-NMR spectrum and element analysis.2. Four coordination polymers synthesized by solvothermal reactions:Solvothermal reactions of 4,4’-[benzenetriyltris(canbonlimino)](benzoate) acid (H2CBDB) and metal ions [Cd(Ⅱ), Zn(Ⅱ), Ni(Ⅱ)] afforded four complexes Cd(CBDB)(H2O) (1), Zn(CBDB)(H2O) (2), Zn2.5(CBDB)(OH)3 (3) and [Ni(CBDB)(H2O)2]·H2O (4). Complex 1 features a 3D close packing architecture consisting of dinuclear cadmium clusters and bridging ligands. In complex 2,2D coordination layers are stacked into a 3D supramolecular architecture through hydrogen bonds among amide groups. Complex 3 also displays a 3D close packing architecture featuring 2D zinc-hydroxide layers. A remarkable feature of complex 4 is the existence of zigzag hydrogen bond ribbons. Complex 2 and 3 display fluorescence behavior.3. Interpenetrated 3D metal-organic frameworks:In complexes [Co2(CBDB)2(py)4(H2O)]·2DMF·0.5H2O (5) and [Zn,.5(CBDB)i.25(DMF)(H2O) (HCOO)0.5]·DMF·2H2O (6),5 displays a four-fold interpenetrated 3D architecture consisting of dinuclear cobalt clusters and bridging ligands, and it contains 3D channels. Complex 6 consists of six-nuclear zinc clusters and bridging ligands, which displays a two-fold interpenetrated architecture containing 2D channels. To our surprise, there exist formates in the channels. And it also shows crystal structure transformation, gas adsorption and fluorescence behaviors.4. Four complexes formed via the influence of pyridine:Diffusion of pyridine into the mixture of H2CBDB ligands and metal ions [Cd(Ⅱ), Mn(Ⅱ)] afforded four complexes [Cd(CBDB)(py)2(H2O)]·DMF·C6H5Cl (7), [Cd(CBDB)(py)2 (H2O)]·DMF·C6H6 (8), [Mn0.5(HCBDB)(py)]·DMF (9) and [Cd(CBDB)(py)2]·H2O·CH3OH (10). Complexes 7 and 8 are isomorphous in which lD chains are assembled into 3D supramolecular networks though hydrogen bonds andπ-πstackings. The difference is the the existence of different guest moleculers. In complex 9, pairs of HCBDB ligands link the neighboring Mn(II) ions to form an infinite 1D chain. Complex 10 consists of dinuclear cadmium clusters and bridging ligands and features a 2D layer with rhombic windows. Complex 7 and10 also display fluorescence behavior.