Synthesis Of Metal-Organic Frameworks-based Materials And Their Application In Adsorption And Catalysis

Metal-Organic Frameworks (MOFs) represent a new class of hybrid organic-inorganic surpramolecular materials comprised of ordered networks formed from organic bridging ligands and inorganic metal cations. MOFs have been generated that exhibit the highest known surface areas, the lowest crystal densities as well as tunable pore size and functionality, which can be tailored for specific applications, including gas storage and separation, catalysis, drug delivery and so on. The application can be largely broadened by designing functional MOFs bearing an organic function or introducing the active sites to the MOFs, which act as hosts for a variety of guest molecules.The linear ditopic ligand 2-amino terephthalic acid bearing an anmio group was used as the organic bridging ligand. The carboxylated groups were coordinated with the metal leading the amino groups free, although such free amino group usually strongly coordinates to the metal ion. This could be achieved by controlling the reaction temperature, time, solvent, and different metal cations using solvent thermal synthesis.An In-N-MOF ((Me₂NH₂)In(NH₂BDC)₂·DMF·H₂O) was synthesized in its octahedron single crystal form. X-ray diffraction, elementary analysis, microscope photograph, FT-IR, thermal analysis, and N₂ adsorption analysis were used to identify the structure and character of the In-N-MOF. It has a 3-D porous framework with a 2-fold interpenetration and remaining channel (6.6 A) along the a axis. The amino groups in the ligands point to the channel, and the channel volume was estimated to be ca. 59.1% by PLATON.The In-N-MOF was examined in the high-pressure adsorption of CO₂ at 298 K, showing an adsorption amount of 213 cm³·g^-1 at 4.5 MPa. The isosteric enthalpies of adsorption at zero surface coverage was 30.1 kJ·mol^-1, which was calculated from the low-pressure adsorption isotherms of CO₂ at 273 K and 298 K. The isosteric enthalpies of adsorption was in the range of 25.7-27.2 kJ·mol^-1 at 10-50 cm³ g^-1 CO₂ capacities. The results indicated a strong interaction between In-N-MOF and CO₂. High selectivity for CO₂ over CH4 and H2 were observed. The adsorption amount of CO₂, H2 and CH4 on In-N-MOF was 174 cm³·g^-1, 7.7 cm³ g^-1, nearly zero, respectively under the same condition. This can be related to the charged framework and free amino group pointing to the pore channel, which could interact with CO₂. The particular pore structure of In-N-MOF enhanced the selectivity based on size/shape exclusion.Knoevenagel condensation reaction of benzlaldehyde with malononitrile was employed as a model reaction to test the catalytic activity of In-N-MOF, Due to the accessibility of the basic sites in the pore channel, the substrate was achieved in good yields (76% yield), which was better than a reported MOF IRMOF-3 under the same reaction conditions. The catalyst could be reused. The amino groups were the catalytic active sites, to activate the substrates in the channel.MIL-101 was selected as a host to support Pd nanoparticles through excessive impregnation due to its high surface areas, high porosity and its good chemical and thermal stability. TEM, EDS, AAS, N2 adsorption analysis, PXRD, and XPS were used to identify the component and structure of Pd/MIL-101. The result showed the Pd particles were highly dispersed on MIL-101 with a unified dimension. The MIL-101 support maintained the structure and high surface area and porosity after the impregnation.Water-mediated Suzuki-Miyaura and Ullmann coupling reaction of the aryl chlorides over Pd/MIL-101 catalyst were first studied. 4-chloroanisol was employed as the substrate in the screening of Suzuki-Miyaura coupling reaction parameters over Pd/MIL-101 and a 96% yield was obtained. The addition of tetrabutylammonium bromide (TBAB) enhanced the yield significantly. NaOMe was the optimal base for the reaction, owning to the presence of a small amount of methanol that was formed from the reaction of NaOMe with water. High catalytic activities were observed for chlorobenzene and both electron-rich and electron-poor aryl chlorides in excellent yields under the optimized reaction conditions. For comparison, a commercial Pd/C catalyst and Pd/ZIF-8 were also tested under the same reaction conditions. However, low activities were observed over the two catalysts.Ullmann reaction of 4-chloroanisol was examined under the similar reaction conditions as those used for the Suzuki coupling reactions. An excellent yield of 96% was achieved even when the reaction was carried out in air. Various aryl chlorides could also be efficiently converted to the corresponding products in high yields. The Pd/MIL-101 catalyst could be easily recovered and reused in the Ullmann coupling of 4-chloroanisol for five times without any loss of efficiency. The combination of XRD and TEM analysed of the used catalyst and the leaching test experiments demonstrated the stability of the catalyst.