Design And Synthesis Of Novel Metal- Organic Framework Materials Based On Multi-Carboxylic Ligands With Gas Storage And Separation Properties

Metal-Organic Frameworks (MOFs) has rising as a novel inorganic-organic hybrid crystalline materials over the past two decades. This new type of porous materials can be readily self-assembled from their corresponding metal ions and/or metal containing clusters with suitable organic linkers. The richness of metal ions and organic linkers makes MOFs with highly designability, enabled us to synthesize a large number of porous MOFs of diverse structures and/or topologies. Furthermore, the pore surfaces within MOFs materials can be functionalized through the immobilization of functional organic groups such as -NH2,-OH,-CH3 and open (unsaturated) metal sites. Actually, MOFs have been emerging as one of the most promising materials in the field such as gas storage and separation, heterogeneous catalysis, luminescence and sensing. In this dissertation, we aimed to construct a serial of MOFs with different pore size and funtional groups by the rational design of organic linkers and propose the approaches to preparation of novel MOFs by taking consideration of the properties of metal and the ligands. We clarified and further investigated the relationship between the structure of MOFs and the property of materials in the field of gas storage and separation. Our research realized the increasement of the sepatation selectivity of C2-C1 gas molecules, the uptake capacity of CH4 and C2H2, and the capture ability of CO2 by different MOFs. This study will give a deeper insight to design and prepare MOFs and make MOFs possible to be used as excellent sorbent.Based the organic linker H4BPTPC and copper salt, we have synthesized a rare doubly interpenetrated lil type MOF:[Cu2BPTPC(H2O)2]·(DMF)6·H2O) (ZJU-30) under the condition of solvothermal reaction. The activated ZJU-30a exhibited highly separation of C2-C1 gas molecules at room temperature. Specially, the henry law selectivity for C2H6-CH4, C2H4-CH4 and C2H2-CH4 are 19.5,11.5 and 9.58, respectively. While, the IAST selectivity at 1 kPa are 18.9,9.6 and 8.9 for C2H6-CH4, C2H4-CH4 and C2H2-CH4, respectively. The open Cu2+ metal sites and suitable pore size make ZJU-30a with highly selectivity for C2-C1 gas. In addition, the pore size can be tunable by the framework interpenation.In order to overcome the framework interpetration in ZJU-30, which lead to a relatively low BET surface area, we developed a novel linker H4TPTPC by incorporting the 1,4-dimethoxyphenyl group into the prototype linker H4BPTPC. Under the condition of solvothermal reaction, we construted a novel stu type MOF: [Cu2TPTPC(H2O)2]·(DMA)18·(H2O)19(ZJU-31). Fortunately, the framework of ZJU-31 is non-interpenetrated by incorporating the 1,4-dimethoxyphenyl group. Correspondingly, the non-interpenetrated ZJU-31a has a relatively higher porosity coMPared with ZJU-30a, indcating ZJU-31a exhibited higher working capacity for separation. Meanwhile, ZJU-31a exhibits much more highly separation of C2-C1 gas molecules than ZJU-30a at room temperature. The henry law selectivity for C2H6-CH4、C2H4-CH4 and C2H2-CH4 are 63.9,29.5 and 18.8 respectively. While, the IAST selectivity at 1 kPa are 23.4,22.0 and 22.5 for C2H6-CH4, C2H4-CH4 and C2H2-CH4, respectively.Although the activated ZJU-31a exhibits relatively high surface area, the framework would collapse partilly, which make the measured value far less than the the value in theory. Herein, we have developed a new organic linker of the aromatic tetracarboxylic acid by the partially-enlargement strategy and incorporated it into a novel NbO three-dimensional MOF:[Cu2DPEBTC(H2O)2]·(DEF)8·(H2O)2 (ZJU-32). The activated ZJU-32a exhibits high porosity with the largest BET surface area and pore volume of 3831 m2/g and 1.482 cm3/g, respectively, among those NbO or PtS type MOFs. Accordingly, it can storage quite large amount of CH4 and CO2 under high pressure at room temperature. ZJU-32a can uptake 0.16 g/g CH4 at 300 K and 3.5 MPa, meanwhile, it can adsorp 960 mg/g CO2 at 300 K and 4.0 MPa, resulting a gravimetric capacity of 49 wt%.The strategy of synthesizing polymorphous MOFs which constructed from the same organic ligand and secondary building units (SBUs) provides another approach for investigating the interaction between the framework and gas molecules. To deepen the understanding of the synthetic method of MOFs, we have contructed a novel NbO type MOF:[C26H12O8)(H2O)2]·(DMF)2·(MeCN)3·(H2O)4 (ZJU-7). The activated ZJU-7a displays moderate C2H2 gravimetric storage of 180 cm3(STP)/g at 1 atm and 298K. Meanwhile, ZJU-7a exhibits moderately high CH4 storage of 160 cm3(STP)/cm3 at 3.5 MPa and 298K, achieveing the 89% of the DOE target.To expand our research in synthesizing the NbO type MOFs. We have developed a new organic linker of the aromatic tetracarboxylic acid with pyridyl site, and incorporated it into a 3D NbO type MOF:[Cu2PDDI(H2O)2]·(DMF)4-(H2O)6 (ZJU-5). The activated ZJU-5a exhibits moderately high porosity with BET surface area of 2734 m2/g. The open Cu2+ sites, suitable pore spaces and Lewis basic pyridyl sites within ZJU-5 have enabled this new MOF to take up a large amount of C2H2. The C2H2 storage of 290 cm3(STP)/g is the highest acetylene storage capacity ever reported at 273 K and 1 atm among any porous materials. Furthermore, ZJU-5a exhibits very high CH4 storage capacity, reaching 190 cm3(STP)/cm3 under 3.5 MPa, which has surpassed the DOE target of 180 cm3(STP)/cm3.In order to investigate the iMPact between the functional groups and gas adsorption in framework, we have systematicly synthesized a serials of linkers modified by different groups and constructed four kinds of NbO MOFs with similiar construction to ZJU-5. Among these MOFs, ZJU-8a can uptake more C2H2 of 201 cm3(STP)/g (143 cm3(STP)/cm3) at 298 K and 1 atm, while ZJU-10a has stronger interaction between the framework and gas molecule with the initial Qst of 39.0 kJ/mol. Meanwhile, ZJU-8a and ZJU-9a are more suitable for CO2-CH4 and CO2-N2 separation. ZJU-8a has the larger working capacity, while ZJU-9a has the higher IAST selectivity. However, the initial Qst of ZJU-5a and ZJU-10a are much higher, indicating that the binding sites can play even more important roles than the interaction strengths in enhancing carbon dioxide uptake and thus gas separation selectivities.