Syntheses, Structures And Characterization Of MOFs Based On N, O Ligands And Transition Metals

In the dissertation, we have intruduced in detail the conditions and methods of synthesis, structural features, thermal stability, fluorescent properties of MOFs based on N, O ligands and transition metals. We have prepared the MOFs with novel structures adopting solvothermal synthesis method using multi-carboxylic acid and heterocyclic aromatic ligands including trimesic acid (H3btc), isophthalic acid(H2ipa), pyromellitic acid N,N-di(2-pyridyl)-pyrrolo[3,4]isoindole-1,3,5,7-tetraone (ppt) and 2,4,6-tris(4-pyridyl)-1,3,5-triazine (tpt), and transition metal composed of nickel, copper, manganese, cadmium and so on.We have successfully prepared two organic ligands: ppt and tpt. Furthermore, we have also successfully synthesized six MOFs: [Ni(H₂btc)(Hbtc)(tpt)(H3O)] (1),[Mn(tpt)(ipa)] (2),[Ni(C₁₀H₂O₈)0.5(H2O)2]·2H2O (3),[Cd(C₁₀H₂O₈)0.5(H2O)3] (4),[Cu(C₉H₄O₆)(H₂O)3] (5),[Cd3(C₉H₃O₆)2(H2_O)9]·2H2O (6). Among them, compounds 1 and 2 are comprised of mixed-ligands and compounds 3⁶ only include one type of ligand molecule. Especially, compound 1 displays a 2-D layered structure which is built byη2 coordination mode trimesc acid and helical chain formed by TPT ligands and Ni atoms, in 1, the trimesic acid adoptingη1 coordination mode also is found to modify the helical chain. Compound 2 displays a 3-D network structure with 1-D channel, which is comprised of three 1-D chains including one zigzag chain formed by Mn atoms and TPT ligands, and two mutually perpendicular 1-D straight chains built by Mn atoms and isophthalic acids along different directions. Compound 3 exhibits 3-D network structure possessing the 1-D rectangular channel, which is formed by Ni atoms and pyromellitic acids. Compound 4 with two different sizes caves possesses 2-D layered network structure is built from the transition metal Cd and pyromellitic acid. Compound 5 displays 3-D supramolecular network structure, which is formed by the 1-D zigzag chain built from Cu and trimesic acid via hydrogen bonds. Compound 6 exhibits 2-D layered network structure with diamond channel that is formed by the five-coordinated and six-coordinated Cd atoms and trimesic acid. We also carried out these six compounds thermogravimetric analyses and fluorescence properties, the stability of compound 2 with blue fluorescence is the best. Compounds 1, 3 and 5 exhibit the fluorescence in the near ultraviolet region, and compounds 4 and 6 exhibit purple fluorescence.