With the emission of carbon dioxide (CO2) becoming an international worry due its role in climate change, solutions such as CO2 capture and storage technologies are needed to decrease the emissions. The main proportion of CO2 gas emissions is from fossil fuel combustion in a range of industries, including power generation. To develop the CO2 capture system for these operations, new materials are needed for CO2 capture. Metal-organic framework (MOF) materials have porous crystal structures containing organic molecules (organic ligands) linked to each other by metalcontaining nodes. The large internal surface area can be exploited for the adsorption of small gas molecules, and for this reason MOFs may be ideal candidate materials for CO2 capture and gas separations. Thousands of MOF materials have been reported, with different combinations of the ligands and metals and with the capability of forming many different network topologies. Experimentally it is very difficult to study the gas absorption dynamics, interaction and gas adsorption capacity for the large number of materials. This problem can be solved by simulations. The aim of the thesis is to develop a systematic simulation method to screen the MOF properties and CO2 adsorption capacity and interaction dynamics at different environment. The molecular dynamics (MD) method with parameterised force fields was used to study the interactions between CO2 molecules and one class of the MOFs, zeolitic imidizolate frameworks (ZIFs) with zinc as the metal cation. To develop the model, the atom charges have been developed by using the distributed multipole analysis (DMA) method based on ab initio DFT calculations for molecules and clusters. The intermolecular forces were developed by fitting against the MP2 calculations of small clusters of the metal cations and molecular ligands. In order to evaluate the models I simulated the gas-liquid coexistence curve of CO2 and showed that it is consistent with experiments. I also simulated the pure ZIF structures on changing both temperature and pressure, demonstrating the stabilities of the structures but also showing the existence of displacive phase transitions. I have used this approach to successfully study CO2 absorption in a number of ZIFs (from ZIF-zni, ZIF-2, ZIF-4, ZIF-8 and ZIF-10) using MD. The gas absorption capacity and dynamics have been investigated under 25 bar and 30 bar, 200 , showing a promising uptake of CO2. The results have shown that CO2 capacity is mainly determined by the pore sizes and pore surfaces, in which a higher capacity is associated with a higher pore surface. The intermolecular distance of CO2 inside the pores and channels have been investigated in the saturation state. It has been shown that the distance is approximately 4 Å. The attraction force is from the interaction between CO2 and the imidazolate ligands. In addition, the systematic studies of the saturated ZIF system gave the minimum diameters for CO2 adsorption which is approximately 4.4 Å. This interaction has caused the gate opening effects, with the imidazolate ligands being pushed to be parallel to the CO2 molecules and opening up to allow more gas molecules go through the channels that connect the pore structures. This gate opening effect also explains the phase transition in ZIF-10 caused by CO2 molecules in our simulation, and can be applied to predict phase transitions in other materials with similar structure such as ZIF-7 and ZIF-8. The dynamics have also shown that the gas diffusion velocity is determined by the pore structure as well and by the accumulated layers of CO2 on the surface prior to being pushed in toward the centre of the material layer by layer. The de-absorption processes have also been studied in these materials by decreasing the pressure from 25 bar to 1 bar under at same temperature. The results indicate that the de-absorption is a reverse process of absorption. The structure of ZIF-10 went through a phase transition induced by CO2 recovered after the guest molecules had been released. The de-absorption can be accelerated by increasing the temperature.

Multiferroics and magnetic metal-organic complexes are candidates for sophisticated applications in the future. In thisthesis, the magnetism in BiFeO3 (a multiferroic material with an incommensurate spin cycloidal structure), copper guanidiniam formate (a multiferroic metal-organic complex with a one-dimensional magnetic structure) and CP -RE-COT (a series of \zero-dimensional" single molecule magnets) are discussed. A radio-frequency plasma sputtering thin lm deposition system and a ferroelectric characterisation system were developed for the study of BiFeO3 epitaxial thin lms. A large leakage current was observed in BiFeO3 thin lms, which hindered the investigations on the ferroelectric properties and magnetoelectric coupling in them. An evidence of the spin cycloid in a BiFeO3 thin lm was observed by grazing-incidence small angle neutron scattering. The magnetism of a multiferroic metal-organic complex with a one-dimensional magnetic chain, [C(NH2)3][Cu(HCOO)3], was studied by magnetometry and muon spin spectroscopy. A spin-canted antiferromagnetic order and critical phenomenon in this material were investigated. It was shown that this material possessed an 3D Heisenberg long-range order below 4.6K. The one-dimensional magnetic chain was also studied by muon spin spectroscopy. The correlation length was measured with a eld dependence of H 1. Magnetisation relaxations of a series of single molecule magnets CP -RE-COT (COT = C8H8- CP = C5Me, which show "zero-dimensional" magnetism, were studied using an AC magnetometer and muon spin spectroscopy. Three possible relaxation pathways, including a quantum tunnelling process and two Orbach relaxation processes, were suggested by the relaxation behaviour. The suppression of the quantum tunnelling effect resulting from the entanglement of the ground states, which probably arises from the exchange interactions in CP -RE-COT, was also observed with a 1000 Oe applied magnetic eld. Data that were consistent with long-range magnetic ordering was observed in CP -Dy-COT, which would be the fi rst ever report of long-range magnetic order in a single ion magnet.

The objective of this work was to develop a molecular simulation method with the capacity to represent the synthesis of metal-organic framework (MOF) structures to the extent of being able to accurately predict the MOF structures that form under specified reaction conditions. MOFs are a class of porous, crystalline solids composed of metal-ion vertices coordinated by organic linker molecules. MOFs are created in a self-assembly process in which the building blocks (reactants) retain their integrity. Under different experimental synthesis conditions, a particular combination of building blocks can react to form differing MOF structures. The structure of MOFs confers a large degree of tunability, allowing almost limitless potential for the materials to be designed with the capacity to fulfil the requirements of a specific application. Consequently, MOFs have shown promise for a variety of applications including gas storage, separation and catalysis. Thus, the ability to accurately predict the MOF formed by specifying reaction parameters such as temperature, pH and the concentrations of reactants has great potential because, upon identification of a promising hypothetical structure for a particular application, the synthesis conditions ascertained via the simulation method could be used as the basis for the determination of an experimental synthesis procedure. In addition, a simulation method with the capacity to predict MOF structures affords the opportunity to gain a fundamental understanding of the influence of the experimental synthesis conditions on the structures formed, so as to enable progress towards the rational design of MOFs. In this work, the experimental synthesis of MOFs via self-assembly is modelled using a kinetic Monte Carlo approach. Ideally, simulation of the self-assembly of the building blocks would be modelled atomistically with all atoms in the reactant and solvent molecules represented explicitly. However, due to the prohibitive computational requirements of such a simulation, in this work a “potential-of-mean-force” (PMF) approach was used to represent the solvent implicitly by encompassing the solvent-mediated behaviour in the interactions between building blocks, thereby reducing the computational cost. The PMF approach to the implicit representation of the solvent involved the utilisation of effective pairwise interactions between the constituents of the reactant species. Following extensive testing to ensure that the explicit-solvent behaviour of the reactants could be replicated using the PMF method, this approach allowed computationally efficient implicit-solvent simulations of the synthesis of MOF materials to be performed. Thorough assessment of a method developed to simulate the synthesis of MOFs required investigation of a system which, under different reaction conditions, forms differing structures. In this respect, the cobalt succinates represent an unparalleled test because under different reaction temperatures, reactant concentrations, pH and reaction time, seven different phases have been identified. Furthermore, the parameters within which the different phases form have been clearly delineated experimentally. The method developed has been employed, under the appropriate reaction conditions, to simulate the synthesis of two of the seven identified phases of the cobalt succinates. Whilst still subject to computational limitations, the MOF-synthesis simulation method yields structures characteristic of those expected experimentally under corresponding reaction conditions.

The ability to construct materials that are specialized for specific tasks is an important challenge for the scientific community. A mature field in this right is that of metal organic materials. These materials are infinitely customizable crystalline materials constructed from metals/metal containing nodes and organic multitopic linkers. Numerous subfields of materials research seek to exploit some of the characteristics and seen-nowhere-else properties of metal organic materials. A nascent, yet promising subfield is the use of metal organic materials in water treatment. The diminishing access to safe clean water continues to grow as a worldwide problem. Freshwater reserves are decreasing and the human populations who rely on them are increasing. It is a clear need to revolutionize the way the scientific community treats and delivers safe water. Our research group discovered a metal organic material made from hexavalent uranium and the organic ligand iminodiacetate. This material was coined the UMON for its nanotubular shape (uranium metal organic nanotube) and early on it was proven to be unique in the way it allowed water to enter the tube channel and bar any other species from doing the same. I sought to use this material as a vehicle to learn and discover new ways that metal organic materials could be used in the water treatment revolution. This dissertation will narrate my investigations into specific hypotheses regarding the UMON’s special water properties. Specifically I sought to construct other materials with hexavalent uranium to test whether the presence of uranium was an important factor in a materials discretion for water. I also helped establish new knowledge regarding the UMON itself by discovering its negative thermal expansion and its ability to select for light water (H2O) over heavy water species (D2O, HDO, HTO).

Thesis (M.Ch.E.)--University of Delaware, 2007. / Principal faculty advisor: Brian G. Willis, Dept. of Chemical Engineering. Includes bibliographical references.

Thesis (Ph. D.)--University of Texas at Austin, 2003. / Vita. Includes bibliographical references. Available also from UMI Company.

Thesis (Ph. D.)--University of Texas at Austin, 2003. / Vita. Includes bibliographical references. Available also from UMI Company.

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京都大学 / 新制・論文博士 / 博士(理学) / 乙第13478号 / 論理博第1578号 / 新制||理||1692(附属図書館) / (主査)教授 北川 宏, 教授 吉村 一良, 教授 竹腰 清乃理 / 学位規則第4条第2項該当 / Doctor of Science / Kyoto University / DGAM