Browsing by Subject "methane storage"
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Item Ligand Design for Novel Metal-Organic Polyhedra and Metal-Organic Frameworks for Alternative Energy Applications(2011-10-21) Kuppler, Ryan JohnThe primary goal of this research concerns the synthesis of organic ligands in an effort to create metal-organic porous materials for the storage of gas molecules for alternative energy applications as well as other applications such as catalysis, molecular sensing, selective gas adsorption and separation. Initially, the focus of this work was on the synthesis of metal-organic polyhedra, yet the research has to date not progressed past the synthesis of ligands and the theoretical polyhedron that may form. Further efforts to obtain polyhedra from these ligands need to be explored. Concurrently, the search for a metal-organic framework that hopefully breaks the record for methane adsorption at low pressure and standard temperature was undertaken. A framework, PCN-80, was synthesized based off a newly synthesized extended bianthracene derivative, yet was unstable to the atmosphere. Hydrogen and methane adsorption capacities have been evaluated by molecular simulations; these adsorption isotherms indicated a gravimetric hydrogen uptake of 9.59 weight percent and a volumetric uptake of methane of 78.47 g/L. Following the synthesis of PCN-80, a comparison study involving the effect of the stepwise growth of the number of aromatic rings in the ligand of a MOF was pursued; the number of aromatic rings in the ligand was varied from one to eight while still maintaining a linear, ditopic moiety. The synthesis of another bianthracene-based ligand was used to complete the series of ligands and PCN-81, a two-dimensional framework with no noticeable porosity as evident by the simulated hydrogen uptake of 0.68 weight percent, was synthesized. All of these MOFs were synthesized from zinc salts to reduce the number of variables. No clear relationship was established in terms of the number of aromatic rings present in the ligand and the hydrogen adsorption capacity. However, it was confirmed that the density and hydrogen uptake in weight percent are inversely proportional. Further work needs to be done to determine what advantages are offered by these novel frameworks containing extended bianthracene derivatives. For example, with the highly fluorescent nature of the ligands from which they are composed, both PCN-80 and PCN-81 should be studied for the potential use in the application of fluorescent materials.Item Porous Metal-Organic Frameworks for Energy Storage Applications: Design, Synthesis and Mechanism Studies(2014-05-05) Liu, YangyangThe self-assembly of metal ions and organic linkers could afford 3-dimensional (3D) porous metal-organic frameworks (MOFs). They are promising materials for clean energy applications including carbon capture, hydrogen storage and methane storage. The primary goal of this research is the synthesis and characterization of new MOFs for these applications, and their structure-property relationship studies based on both experiments and simulations. Firstly, a stable magnesium MOF with 1-dimensional (1D) channel structure was synthesized. In-situ powder X-ray diffraction studies reveal its interesting phase transitions properties. After removing coordinated solvent at magnesium chains, this MOF can selectively adsorb CO_(2) over N_(2). Secondly, by varying the conditions in the solvothermal reaction, five MOFs with diverse structures were synthesized from a tetratopic ligand. Hydrogen storage properties were studied for these MOFs. A list of factors including catenation, metal nodes, charge, topology and pore size are evaluated for hydrogen storage application. In addition, four isostructural MOFs with various functionalized pore surfaces were synthesized from a series of di-isophthalate ligands. These MOFs exhibit a new network-topology and very high hydrogen uptake. They also showed reasonable adsorption selectivity of CO_(2) over CH_(4) and N_(2). Finally, high pressure methane uptake properties have been studied both experimentally and computationally for the series of isostructural MOFs with varying functional groups. All showed very high methane storage capacity at 298 K, 65 bar. Structure-property relationships were established for these MOFs, and simulations were employed to understand the mechanism of methane storage in MOFs. The role of copper paddlewheels and other adsorption sites for methane was evaluated. By thorough studies and careful analyses of simulation and experimental data, we proposed three novel mechanisms for methane storage in MOFs. Significantly, with the help of the mechanism studies, another two MOFs were designed, synthesized and discovered to have even higher methane storage capacities. Ligand design has been a powerful tool in synthesizing new MOFs. Besides surface area, pore size has been discovered to be a key factor for gas storage capacities of MOFs. These findings could serve as guidance for rational design of better performing materials for clean energy applications.