| Metal-Organic Frameworks (MOFs) is a new class of nanoporous materials. Due to their large surface area and porosity, easy synthesis, high thermal stability and the controllable chemical modification for certain targets, MOFs have been shown very promising applications in the fields of gas storage, separation, catalysis, biochemistry, and pharmacy. However, it is difficult to carrry out systematical study by experiment because of the chemical diversity and complex structure of MOFs. In this thesis, we choose several porous solids as a representative of MOF materials:(â…°) Cu-BTC, whose pore size is about 9.5X9.5 A, not only has a similar three-dimensional pore structure with another well-known material MOF-5, but also possesses a particular structure with side pockets and a large number of unsaturated metal sites. This material is one of the hot MOFs that has been widely studied toward gas storage and catalysis research, (â…±) Zeolite-like Metal-Organic Frameworks (ZMOFs) is a special kind of MOFs with a negatively charged framework, large pores, wide window, and high chemical stability in aqueous solution and so on. In this thesis, the main research topics about these two types of materials are summarized as the followings.1. We synthesized two kinds of zeolite-like metal-organic frameworks, usf-ZMOF and sod-ZMOF. The lager extra-frmawork organic cations ere substituted by the smaller metal ions through ion-exchange method. Then the adsorption properties of CO2 gas in the materials before and after ion-exchange were measured. The experiment data indicate that the specific surface area and the CO2 adsorption capacity are both increased for the material exchanged with lithium ions, which is in good agreement with the predictions from the molecular simulations.2. We have tried to find the best approach for the synthesis and activation of Cu-BTC so as to obtain a larger surface area and higher porosity. At the moment, since MOFs are generally synthesized through the hydrothermal mehtod, that is, in solvents at a certain temperature and pressure, the voids of the materials are fully filled with the solvent molecules. In this work, the remove of the solvent molecules from the pores as far as possible was set as a research goal. Because of the surface tension of solvent existing in the framework, the conventional drying method tends to induce the collapse of the framework. The aim of supercritical drying is to make the solvent to reach its own critical point in the process of drying by controlling the pressure and temperature. As there is no obvious surface tension in this process, the solvent can undergo the supercritical transition from the liquid to vapor while framework structure of the materials remains integrity. This idea was employed to activate Cu-BTC in this work. The results showed that the surface area of the material treating by the supercritical drying is larger than the conventional drying.3. We have successfully prepared a dense Cu-BTC membrane using a copper mesh after treatment as the base. The copper mesh treated with oxidation is not only a modification both on the surface, but also provides a divalent copper, leading to a double copper source environment for the growth of Cu-BTC crystals. We may expect to apply this method to prepare other MOF membranes by choosing the corrsponding metal material as the substrate for the selected MOFs. |
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