Synthesis, Structures And Properties Of Metal-Organic Frameworks Based On Rigid Carboxylic Acid Ligands

The design and synthesis of new functional metal-organic framework in coordination chemistry, supramolecular chemistry, crystal engineering is one of the active research fields in recent years, due to their special properties in new topology, photoelectricity, magnetism, molecular recognition and catalysis etc. In this thesis, we try to synthesize novel coordination complexes by use of rigid carboxylate ligands to assemble with transitional metal ions or rare-earth metal ions. The assembly of rigid carboxylate with metal ions yielded6novel metal-organic complexes. All complexes have been determined by single-crystal X-ray diffraction, elemental analyses, XRPD analysis, thermal analysis, Gas adsorption and fluorescence spectroscopy. There are following five chapters.In chapter1, a brief introduction of the coordination chemistry, metal-organic framework and other basic concepts and Application.The chapter2, two porous metal-organic frameworks (1and2) with a fsc topology based on mixed ligands have been assembled and characterized. The different pillared ligands (pyrazine for1and4,4’-bipyridine for2) significantly influence the pore size of the frameworks. Gas uptake measurements reveal that complex1possesses higher H2,CO2,and CH4uptake capacities than2, although the surface area of1is lower than that of complex2. These results further experimentally prove that the pore size plays an important role in gas uptake in porous MOFs, and the slit pore with a size of6A exhibits stronger interactions with gas molecules.In chapter3, due to their tunable structure and porosity, metal-organic frameworks have provided a new platform for fluorescence sensor and adsorptrion/separation of gas or organic molecules. Many studies have focused on sensing metal ion, anion, or organic molecules through fluorescence quenching or enhancement of MOFs, seldom are reported on pH-fluorescence sensor. Furthermore, highly solvent-dependent selectivity and degradation to dye molecules based on functional MOF has never been explored to date. Here we report a multifunctional Eu MOF,[H3O][Eu3(HBPTC)2(BPTC)(H2O)2]·4DMA (H4BPTC=3,3’,5,5’-biphenyltetracarboxylate). The luminescence intensity of COMPLEX-3is strongly correlated with the pH value in the pH range from7.5to10.0, and a linear relationship between pH value and fluorescent intensity is observed. Another attractive property of Complex-3is that its Li-exchanged form, Li-3, possesses solvent-dependent selectivity and degradation to rhodamine B. The high-efficient degradation or decolorization of rhodamine B with long-term stability and activity makes Li-3have potential advantage in treating rhodamine B pollutant.In chapter4, three3D manganese-organic frameworks, Mn2(BPTC)(dmf)2(H2O)·dmf·3H2O(4), Mn2(BPTC)(bipy)(dmf)·dmf·H2O (5), and Mn2(BPTC)(phen)(dmf)·EtOH (6), have been solvothermally synthesized by using3,3’,5,5’-biphenyltetracarboxylic acid (H4BPTC). All complexes are characterized by PXRD, EA, IR and TG. The results show that they all bear PtS topology with (42.84)(42.84) for the vertex symbols of the planar and tetrahedral nodes, in which BPTC ligand is considered as a square-planar4-connected linker, and every binuclear SBU connected to four BPTC ligands is simplified into tetrahedral4-connected node. Since three coordination sites of one metal center of SBU are occupied by coordinated solvent molecules, complex1exhibits low stability. After substituting2’2-bipy or1,10-phen for two coordinated solvent molecules, complexes2and3display evidently higher structure stability. The magnetism property of complex5is also discussed in detail.In chapter5, the conclusions and prospects.