Synthesis, Structures And Characterization Of Novel Porous Metal-Organic Carboxylate Frameworks

Porous materials have attracted much attention of scientist all over the world be-cause of their prime importance in peoples'social production and daily life due to their properties of gas storage, ion exchange, molecular seperation and asorption, ca-talysis and sensings. Metal-organic frameworks (MOFs), as the third generation of crystalline porous materials, usually means a kind of crytalline materials with period structures constucted from rigid or half-rigid organic ligands and metal ions or metal clusters by coordination bonds through a self-assembly process. MOFs have crystal structures like zeolites, but usually bigger surface areas and porous structures. MOFs can be partly targeted synthesized due to their organic component part, meanwhile with unique multifunctional properties in optic, electric, and magnetic fields. There-fore, the design, structures and properties of MOFs develop rapidly as an interdiscip-linary hot field recently.Due to their unique designable and adjustable, in last decades many research groups have focused on the synthesis of MOFs. People have accumulated a lot of ex-perimence and knowledge about the rule to synthesize MOFs, and the design and synthesis of MOFs has developed to an important part of molecular engineering. However, to realize the various multifunctional properties of MOFs and fit the com-plicated practical applictions, the design and synthesis of MOFs with unique porous properties are not enough. This thesis started from the porous properties of MOFs, selected rigid carboxylic ligands, aim to synthesis of MOFs with unique porous prop-erties and accomulate valuable experimental basis. The synthesis methods in this the-sis include amine diffusion and solvent volatilization under amient temperature, hy-drothermal and solvothermal conditions. The structures of compounds are confirmed mainly by single crystal resolution. The stability of compounds are confirmed through powder x-ray diffraction and thermogravimetric analysis. The porous properties are characterized by adsorption. The study mainly includes the following four aspects:(1) Chirality is the most normal phenomenon in nature, and homochiral separa-tion and catalysis are of great significance in science. MOFs offer new opportunities to obtain chiral porous materials. In Charpter 2, we synthesized three porous MOFs using the low-symmetric three-connected ligand 3,5-pridinecarboxylic acid (3,5-PDC) and metal Mn, Co, Ni. Compound 1 is constructed from Mn, and is a homochiral framework with homochrial channels. The diameter of helical channels is about 7 ?. Compound 2 and 3 constructed form Co, Ni relatively have the same structure, which is non-central. The structure can be considered as three-connected net. The Schl?fli symbol is {82?10}, which belongs to a rare LIG topology. We studied the stability of these three compounds. Meanwhile, we studied the magnetism of compound 1, which exhibits a normal antiferretic behavior.(2) 3,5-PDC is planar three-connected ligand, which is tend to form (6,3) layer with transit metals Zn (compound 4) Cd, Mn. Pillar is a normal strategy to construct three dimensional (3-d) MOFs. Our strategy is pillaring this kind of (6,3) layer by neutral liner ligand 4,4'-bipridine to obtain 3-d open porous structures. In Charpter 3, we pillared the (6,3) layers constructed from Zn, Cd and 3,5-PDC. Interestingly, the layer of Zn is pillared to a bilayer structure (compound 5). The layer of Cd is pillared to a 3-d open framework belonged to BN topology (compound 6), which realized our strategy successfully. After the stability study, we found compound 5 is stabler than compound 6, which disagrees with our general understanding that compound is stab- ler with higer dimension. Meanwhile, we studied the photoluminescent properties of compound 5,6.(3) To obtain MOFs with higher heat and hydrothermal stabilities and multifunc-tions, in Charpter 4, we used the ligand 4,4'-(hexafluoroisopropylidene) bis(benzoic acid)) (H2hfipbb) containing CF3 and constructed six MOFs, compound 7-12. Com-pound 7, 8 have the similar structures, which is a homochiral 3-d framework with 1-d hexagonal homochiral fluorine-coated channels and 1-d rhombus channels. Com-pound 9 is a framework constructed from paddle-wheel Co units with 1-d rhombus channels. Compound 10, 11 have the similar 2-d layer structures with 1-d rhombus channels parallelled with the layers. Compound 12 is a condensed MOF constructed from complicated belt Co secondary building units. All these MOFs have high stabili-ty, especially compound 7 which is stable under 400oC or boiling water. The porous study on compound 7 indicates it is a superhydrophobic microporous material, but has affinity to small molecules with–CH3 or CF3. Because of their special metal center, the magnetism of compound 8 and 12 have studied.(4) MOFs are a candidate of hydrogen storage materials. Open metal sites in the framework are important to adsorb gas molecules. To compare different metal open metal sites, in Charpter 5, we have synthesized two compounds with the same struc-ture to HKUST-1 with metal Mn and Co (compound 13, 14, relatively). We also stu-died the synthesis of another compound (compound 12) with the same structure to HKUST-1. However, we found all three compounds are not so stable after the termin-al molecules are removed. The gas sorption measurement is needed a better method to handle their pores.(5) In the synthesis process of MOFs, in situ organic reactions occur and new organic ligands generate sometimes. In Charpter 6, we attempted to synthesize MOFs by linear N-containing ligand 1,4-diaza - bicyclo [2.2.2] octane (DABCO). Interes-tingly, in situ redox reaction occured in the formation of MOFs and DABCO was oxided to 1,4-diaza - bicyclo [2.2.2] octane -N,N'-dioxide (DABCO-N,N'-dioxide) under mild conditions. DABCO-N,N'-dioxide as two-connected node link two six-coordinated Cd to form a three dimensional structure (Compound 16) with a non-interpenetrated pcu topology.