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Polymers of Intrinsic Microporosity (PIMs) combine the desirable processability of polymers with a significant degree of microporosity generated from the inefficient packing of their rigid and contorted structures. They are attracting attention for a variety of applications including as membrane materials for gas separations. Over the last 30 years, membranes have become an established technology for separating gases and are likely to play key role in reducing the environmental impact and costs of many industrial processes such as O2 or N2 enrichment from air, natural gas upgrading and hydrogen recovery from ammonia production. This thesis describes the synthesis of a series of novel PIMs, primarily PIM-polyimide structures (PIM-PI) and investigates their potential in such applications. In particular, it focuses on the design and synthesis of solution processable PIMs in order to study how structural differences affect the gas permeability. The first section describes the synthesis of a variety of PIM-PIs using large bulky diamines derived from spirobisindane (SBI) and biphenylfluorene (BPF) structures which are useful monomers for achieving high BET (Brunauer-Emmett- Teller) surface areas (> 650 m2 g-1). The second section describes a whole series PIs based on novel and literature based Tröger’s base (TB) diamine monomers. Most of these exhibited good solubility, excellent thermal stability and intrinsic microporosity, with apparent BET surface areas in the range 450-739 m2 g-1. Notably, a polyimide derived from Me2TB and pyromellitic anhydride demonstrates gas permeability data above the 2008 upper bounds for important gas pairs such as O2/N2, H2/N2 and H2/CH4. The third section aims to enforce rigidity within the polymers further by incorporating differently substituted monomers based on rigid ethanoanthracene (EA) units. This includes the formation of a novel EA-EA based PI with an exceptionally rigid polymeric structure, possessing a BET surface area of 694 m2 g-1. In addition to very high permeability, this polymer demonstrates improved gas selectivity due to its enhanced performance as a molecular sieve, placing it amongst some of the highest performing polymers to date. The final section looks at other ways in which rigidity can be enforced including the formation of TB-polymers and thermally rearranged (TR) polymers and assesses their potential for future investigations.

Nanoporous metal-organic frameworks (MOFs) have attracted tremendous interest due to their potential applications in gas-storage, gas separation, gas sensing, and catalysis. MOFs consist of metal-oxygen polyhedera interconnected with a variety of organic linker molecules, resulting in tailored nanoporous materials. With a judicious choice of organic linker groups, it is possible to fine-tune size, shape, and chemical functionality of the cavities and the internal surfaces. This unique structural feature offers unprecedented opportunities in small-molecule separations as well as chiral separations and catalysis. Prototypical iso-reticular metal-organic frameworks (IRMOFs) have been extensively studied among MOFs due to the simplicity of their synthesis and the variety of their potential applications. IRMOFs are a specific series of metal-organic frameworks developed by Yaghi and his coworkers. All IRMOFs are composed of oxygen-centered Zn4O tetrahedra interconnected with dicarboxylate linkers, forming a cubic type three dimensional (3D) porous network with high surface area. Despite a great deal of research in the synthesis and characterization of MOFs, there have been relatively few reports on the development of their applications, such as the fabrication of MOF thin films and membranes for gas separations. This is mainly due to the challenges associated with relatively difficult heterogeneous nucleation (seeding) and growth of MOFs on supports, and crack formation compared to their counterparts. Thin films and membranes of MOFs have great potentials for applications in membranebased gas separations, reactors, chemical sensors, and nonlinear optical devices. In this dissertation, the fabrication of IRMOF-1 membrane using a novel seeding method and its gas diffusion properties has been demonstrated. Introduction of the new seeding method for MOFs using microwaves resulted in well inter-grown IRMOF membranes showing Knudsen type transport of small gases through its pore. The heteroepitaxial growth of one IRMOF on another produced multi-layered IRMOF membranes. In addition, postsynthetic modification (PSM) of IRMOFs created functionalized membranes with enhanced stability against water as well as reduced crack formation during membrane fabrication. Lastly, hierarchical IRMOFs with improved CO2 adsorption properties were synthesized via PSM with cyanuric chloride.

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Thesis (Ph.D.) in Materials Science--University of Maine, 2004. / Includes vita. Includes bibliographical references (leaves 112-122).

There is a pressing need for advanced solid-state materials that can be implemented in industrial gas separation processes to achieve separations with a significantly reduced energy input compared to what is typically required from current technologies. Although certain porous materials like zeolites bear some commercial significance for gas separation; their inherent lack of tunability limits the extent to which these materials may be exploited in industry. Zeolite-like Metal-Organic Frameworks (ZMOFs) are a sub-class of Metal-Organic Framework materials (MOFs) that show a structural semblance to zeolites while possessing the tunability advantages of MOF materials. ZMOFs which are topologically similar to certain zeolites can be functionalised and tuned in numerous ways to improve their gas separation properties. In this work, indium-based sod-ZMOF was tuned by cation-exchange and then characterised by different experimental tools such as single-crystal x-ray diffraction, elemental analysis and gas adsorption. It was found that various parameters like the choice of cation, the concentration of salt solution and the choice of solvent had a significant bearing on the cation-exchange of sod-ZMOF and its subsequent adsorption properties.

Matrimid was utilized for the preparation of membranes with asymmetric structures. A combination of well-known solvents for Matrimid which include 1- methyl-2-Pyrrolidone (NMP), tetrahydrofuran (THF), dichloromethane, tetrachloroethane as well as non-solvents n-butanol, xylene, and acetic acid were used. Cast solutions were prepared at room temperature for different combinations and compositions of polymer/solvent/non-solvent systems. PEG and Octa-(amino phenyl) POSS were introduced in some of the cast solutions. The membranes obtained were characterized by permeation test for gas permeabilities and selectivities, Scanning Electron Microscopy (SEM) and Nuclear Magnetic Resonance (NMR) Spectroscopy. The gas permeation test showed that the use of mixture of dichloromethane and tetrachloroethane as solvents with xylene non-solvent and acetic acid as stabilizer gave membranes with very high gas selectivity of 133 for CO2/N2 and 492 for CO2/CH4. Also, cast solutions containing PEG resulted in membranes with slightly enhanced selectivities from 30 to 42 for CO2/N2. Permeation results for CO2, N2 and H2 and the selectivities for gas pairs such as CO2/N2, CO2/CH4, are discussed in relation to the effect of pressure on the membrane permeance, they are also compared with existing results.

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