Design, Synthesis And Structural Characterization Of New Metal-organic Frameworks Based On Multibentate Carboxylic Ligands

Metal-organic frameworks(MOFs) are constructed by metal ions or metal clusters and organic ligands through strong coordination bonds. Because of their large surface area, permanent porosity, easily tailorable structures and functions as well as infinite structures, MOFs have potential applications in gas adsorption and storage, catalyst, and proton conduction. Modify the ligand acid through direct synthesis or postsynthetic modification and choose the secondary building units(SBUs) with different configurations as metal nodes can greatly enhance the diversities of MOFs.In the first part, through ligand modification, two V-shape ligand acid, [1,1’:3’,1’’-terphenyl]-4,4’’-dicarboxylic acid(H2TDBA) and 4,4’-(pyridine-2,6-diyl)dibenzoic acid(H2PDDA) were designed and synthesized. They share similar structure, differently, the central ring of H2 TDBA is benzene ring, while that of H2 PDDA is pyridine ring. The existence of H atoms in the central ring of H2 TDBA lead to relative large steric hindrance, thus, the dihedral angles of H2 TDBA between the central ring and two side benzenes are larger than those of H2 PDDA. The assembly of them and quadrangular Cu2O2(COO)4 SBUs under the same conditions yielded two new MOFs, [C u(TDBA)(DMA)2](BUT-221) and [Cu3(PDDA)3(DMA)2(H2O)](BUT-223) with different structures, respectively. Single crystal X-ray diffraction shows that different configurations of the two ligands lead to the different structures of the two MOFs. From topological view point, the Cu2O2(COO)4 SBU can be served as a 4-connected node and the two ligand acids serve as the edges, BUT-221 can be simplified as a a 2- fold parallel interpenetrating Sql net; while BUT-223 can be simplified as a Kgm net.In the second part, a new desymmetrical ligand acid, 5-(2,6-bis(4-carboxyphenyl)pyridin-4-yl)is-ophthalic acid(H4BCPIA) was designed and synthesized. Solvothermal reactions of H4 BCPIA with Cu(NO3)2·2.5H2 O or In(NO3)3·5H2O in N,N-dimethylformamide(DMF) or N,N-dimethylacetamide(DMA) yielded two three-dimensional(3D) MOFs: [C u2(H2O)2(BCPIA)](BUT-20) and(Me2NH2)[In(BCPIA)](BUT-21) with different structures, respectively. In BUT-20, each twelve C u2(H2O)2(COO)4 SBUs are connected together by six BCPIA4- to form an octahedral cage. Each face of the cage unit is shared by other octahedral cages to form a 3D framework; while in BUT-21, In(COO)4 nodes are linked by the ligands to form again a 3D framework with two types open channels in the a axis. Different linkage configurations of the two metal-containing nodes, quadrilateral C u2O2(COO)4 and tetrahedral In(COO)4, lead to distinct structural networks of BUT-20 and-21, respectively. From topological view point, the two ligand acids and SBUs can be served as 4-connected nodes, BUT-20 can thus be simplified as a 4-connected net with the Nbo-type topology; while BUT-21 can be simplified as a 4-connected net with the Unc-type topology.