Fabrication of metal organic frameworks composites using the space engineering for gas storage and electrical performance

Abstract

From the industrial revolution, the usage of the fossil fuels such as coal, gasoline and natural gas were gradually increased and they allow to sharply develop the civilization. However, the fossil fuels have oc-curred severe environmental problems for example greenhouse effects taking place the increasing the sea level and a respiratory disease to human. Under these condition, many researchers have studied about the alternative energy sources such as wind power, solar cell, water power and geothermal heat, however, these alternative energy sources have low efficiency and lack of stability for using the industrial level. Also, the fossil fuels will be used as a main energy sources and the portion of fossil fuels still high in the future. Because of that we should construct the sustainable energy circulation system which has capturing the carbon dioxide and byproduct from the combustion engine. After capturing the carbon dioxide and byproducts, they are converted to the reusable energy sources such as methane and methanol. Furthermore, the energy storage system from the solar cell is important part to maintain the sustainable energy circulation system. In these researches, we have studied about the Metal Organic Frameworks (MOFs) for capturing the carbon dioxide and storing the methane. In addition, the MOFs are applied to the energy storage system as a lithium sulfur battery. For solving the energy problems, we applied to the new concept, space engineering in materials, for improving the efficiency of gas storage and energy storage. As following the concept of space engineering, we have designed and created nano-sized space after then we have utilized the nano-sized space using the functional groups. During the 1990s, prof. Omar M. Yaghi suggested the MOFs for high storage effi-ciency of hydrogen. After that the MOFs have also utilized to capturing the carbon dioxide and storing the methane which have high capturing and storage capacities. The MOFs have a lot of sites to adsorb the hy-drogen losing the vibration energy because they have a high specific surface area and porosity. The MOFs have high gas capturing and storage efficiency in the low temperature but it has still limitation for apply to the industrial applications in the room temperature. In the Chapter 2, we have fabricated the (Pomegranate) pmg MOF-5 which has different two organic linkers, terephtalic acid and 4-(dodecyloxy)benzoic acid (DBA) and it has unique structure, the meso- and macopores are fabricated in the core of crystal and the core area is surrounded by micropores. The pmg MOF-5 has “self-sequestering gas storage mechanism” because of its unique structure. We have proved the crystal growth and self-sequestering gas storage mechanism by using the SPring-8 synchrotron. Also, we have carried out the gravimetric gas adsorption of carbon dioxide and methane in high pressure at room temperature. In addition, the capturing of methane is another important issue in the environmental problems be-cause the methane emit the lower carbon dioxide than fossil fuels after burning in the combustion engine. Furthermore, the methane is applied to the vehicles as the compressed natural gas (CNG) so it need to effi-ciently storage methane. In the Chapter 3, we will discuss about the methane storage in the nHKUST-1 MOF-5 which is novel MOF composites consisting the two different MOFs. The nHKUST-1 and MOF-5 have a different oxide units and organic linkers so we can growth the core/shell structure using the nHKUST-1 and MOF-5. However, we fabricated the nano-sized HKUST-1 and it was embedded in bulk size MOF-5. The structure of $nHKUST-1 \subset MOF-5$ was prove by various experimental measurements and it was applied to the methane storage in high pressure at room temperature. As mentioned above, the MOFs have many advantages and they can apply to the other applications such as electrical performance. However, the MOFs are known for semi-conductive material which is insula-tor and doesn’t flow the electrons through the MOFs frame structures. For overcome these aspects, our group recently suggested the new MOF composites which are consisted of the nano-sized MOFs and graphene. Also, this composites was applied to the supercapacitor which has higher energy density and stability than com-mercialized supercapacitor using the activated carbon. This is because nano-sized crystal and graphene im-prove the conductivity and then utilization of all of the surface and porosity. In the Chapter 4, we will discuss about the sulfur battery using a Zirconium - MOFs which have a high cycle stability during the dis-charge/charge cycle reactions. These improved results arise from the functional group, nitrogen $sp^2$ orbital, and high pore volume of the Zr-based MOFs. In addition, we have proved the chemical interaction between nitrogen $sp^2$ orbital and lithium polysulfide using the visualization process, FT-IR, XPS and in-situ spectro-elctrochemical measurements. All of these researches mentioned above are related to the space engineering of MOFs for improving the efficiency of gas storage and electrical performance. And then, we carried out the experiments for proving the mechanism and hypotheses.