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Synthesis, Structure And Properties Of Novel Metal-Organic Carboxylate Frameworks

Posted on:2010-01-05Degree:DoctorType:Dissertation
Country:ChinaCandidate:X J ZhaoFull Text:PDF
GTID:1101360272997296Subject:Inorganic Chemistry
Abstract/Summary:PDF Full Text Request
Recent ten years, metal-organic frameworks (MOFs), a kind of functional molecular material, have attracted much attention for their flexible tailoring, various topologies and promising application in ion-exchange, adsorption, molecular recognization, catalysts along with optics, electrics, magnetism and enantioselective separation. Metal-organic frameworks with rigid open frameworks, zeolite-like materials, possess not only porous phases similar to inorganic zeolites but also better performance in gas adsorption and storage than traditional zeolites. Along with the design and preparation of MOFs of larger channels and cavities, much attention has turned to synthesize metal-organic frameworks with the promising applications in optics, electric, magnetism, enantioselective separation and catalysis by selecting functional metal ions and organic ligands with specific groups.According to the principle of molecular engineering, we have focused our study on the synthesis, structures and multifunctional properties of MOFs with charming topologies. In this dissertation, we have prepared 15 new MOFs by using different organic carboxylate ligands, and analyzed their topology structures as well as explored their multifunctional properties. These results will be introduced from the following three issues:(1) New materials with rare earth element are of great interests due to their many research groups have choosen rare earth elements as metal centers to assemble metal organic frameworks and a number of novel frameworks have been synthesized. However, it is really difficult to obtain open frameworks with permanent porosities for their high-coordination number and flexible coordination geometry compared with traditional metals, especially under hydrothermal conditions. Considering the functions of metal-organic frameworks and the synthesis conditions, we designed and synthesized six metal-organic frameworks based on rare earths by choosing multidentate organic carboxylate ligand, H3CTC, and using mild solvent vapor conditions. We also investigated their topology, gas storage, adsorption, optical and magnetic properties coming from rare earth metal centers. For six compounds, compound 1 shows Tb3+ characteristic emission in the range of 460 ~ 660 nm; compound 1-5 are equivalent to the adsorption of about fifteen water molecular or seven methanol molecules per unit cell; compound 7 could separate methane and carbon dioxide after removing all of the free moleculars in its channel; the compound 1 and 7 exhibit the antiferromagnetic interaction between the Tb3+/Yb3+ ions.(2) Normally, the metal-organic frameworks (MOFs) are constructed by transition metals / rare earth metals and multidentate ligands containing oxygen or nitrogen atoms. The metal-organic frameworks consisting of the ligands containing oxygen atoms, such as fumaric acid, and the ligands containing nitrogen atoms have attracted much attention. But the reports about the metal-organic frameworks, consisting of fumaric acid and another organic carboxylate ligand togther, are rare. Basing on the research of the metal-organic frameworks contaning fumaric acid, we designed and synthesized two kind of metal-organic di-boxylate frameworks under the mild solvent vapor condition and solvothermal condition respectively, by choosing (fumaric acid + acetic acid) and (fumaric acid + 1, 3, 5- benzenetriboxylate acid) as organic carboxylate ligands. We analyzed their structures and topologies, and characterized their powder XRD curves, and IR spectrum and fluorenscen properties.(3) In order to obtain large pores and caves, much attention is attracted to synthesizing the metal-organic frameworks by developing the organic ligands. And the ligands contining aromatic and unsaturated groups are the one of the best choice. But the research of the metal-organic frameworks constructed by flexible carboxylate ligands containing unsaturated groups is less than rigid or aromatic carboxylate ligands. We synthesized 3-D metal-organic frameworks with 1, 2, 3-propylenetriboxylate acid as organic ligand under the mild temperature condition. And we characterized their crystal structures, powder XRD curves, IR and fluorescence pretrum.
Keywords/Search Tags:metal-organic frameworks, crystal structure, topology, adsorption, gas storage, fluorescence, magnetism
PDF Full Text Request
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