| Metal-organic frameworks (MOFs) are of some potential applications, such as gas storage and separation, luminescence, electronics, magnetism and catalysis due to their fascinating topology and ultra-high surface areas. How to design and synthesize functional MOFs becomes the bottleneck of the development of such porous materials. Compared with traditional inorganic porous materials, MOFs have superior pre-designability and post-synthesis modification that can effectively modify the cavity sizes and control the functional groups. Currently, the common synthesis method of ligand includes organic synthesis and in situ reaction. The ligands obtained by organic syhthesis can be derictly used to construct MOFs. In situ reaction refers to the precursor into new ligands that can instead of the precursor to build MOFs. Metal ions as the other building component can be chosen purposefully or be obtained by metal ion exchange process. Metal ion exchange method is one of post-synthesis modification approaches, which can achieve the goal of designing synthetic MOFs.In this thesis, we designed and synthesized four multi-carboxylate ligands (H3L1, H3L3, H4L4, H6L5). Twelve novel MOFs were obtained by the assembly reactions between the ligands and transition metal ion (Zn2+, Cd2+, Mn2+, Cu22+) or lanthanide metal ions (Ce3+, Pr3+, Eu3+, Tm3+, Yb3+). All complexes have been characterized by single-crystal X-ray diffraction, thermal analysis, XRPD analysis and elemental analyses. Their properties of fluorescence spectroscopy, gas adsorption, catalysis, dye adsorption and magnetic were investigated. The contents of this dissertation are as follows:1. Two 3D non-interpenetrating porous metal-organic frameworks (1 and 2) were synthesized by employment of a C3-symmetric ligand (H3L1) to assembly with Cd2+ and Zn2+. Both 1 and 2 have M3 clusters as SBUs. Interestingly, when complex 2 was prepared with H3L1, in situ decarboxylic reaction of the initial H3L1 occurred to generate a new ligand (H2L2). Significantly, complex 1 with larger channels is unstable upon the removal of guest molecules, while activated 2 exhibits higher stability and permanent porosity. Our results presented here further indicate that the stable SBU is crucial to the assembly of porous MOF with permanent porosity.2. An anionic metal-organic framework (3) was successfully prepared by the reaction of MnCl2 with H3L1 under solvothermal condition.3 exhibits the exchange of metal ions from Mn to Cu in a single-crystal-to-single-crystal manner to generate 4, which could not be obtained by direct solvothermal reaction of CuCl2 and H3L1. Both 3 and 4 exhibit similar properties for gas sorption, dye separation and catalytic activity. However, the magnetic behaviors for 3 and 4 are distinct due to the metal-specific properties. Below 47 K,3 exhibits a ferromagnet coupling but 4 shows a dominant antiferromagnet behavior.3. Five lanthanide metal-organic frameworks (Ce (5), Pr (6), Eu (7), Tm (8), Yb (9)) have been synthesized by H3L3. Complexes 5-9 exhibit similar 1D channels through the linkage of the Ln-carboxylate chains by the backbones of H3L3 ligands. The channels for complexes 5 and 6 are occupied by coordinated NMP molecules.7 shows a potential application for the luminescence sensing of small organic molecules. Moreover,9 exhibits selective adsorption of CO2 over N2 and CH4 and catalytic activities toward the cyanosilylation reaction.4. Two porous metal-organic frameworks (10 and 11) were synthesized by the reaction of Cd(NO3)2 and H4L4 under different solvent system. Complex 12 was built by the H6L5 ligand and Cu2+, which was constructed by packing of nanosized cuboctahedral, truncated tetrahedral, and truncated octahedral cages. Compared with the ligand (4,4’,4"-(methylsilanetriyl)tris-(triphenyl-3,5-dicarboxylic acid)), H6L5 have longer branched-chain and complex 12 exhibits high surface areas and gas sorptions for N2. |
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