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<p>Metal-organic frameworks (MOFs) are considered as a type of very useful materials for the gas separation/purification industries. However, control over the growing position and growing shape of the crystals remains a challenge and must be overcome in order to realize the commercial potentials of MOFs.</p> <p>In this thesis, a method based on interfacial coordination is developed to address this issue. Zinc-benzenedicarboxyl (Zn-BDC) is chosen as a model system for the proof of concept. In a typical liquid-liquid interface protocol, the MOF precursors, zinc nitrate [Zn(NO3)2] and terephthalic acid (TPA or H2BDC), and the catalyst, triethylamine (TEA), were dissolved into two immiscible solvents, dimethylformamide (DMF) and hexane, respectively. The reaction site, i.e. the MOF growing position could thereby be confined at the interface of the two solvents. It was found that a free-standing membrane could be formed with the combinations of high Zn-H2BDC and low TEA concentrations. The combinations of low Zn-H2BDC and high TEA concentrations yielded MOF particles precipitated out from DMF. Similar results were obtained by changing the liquid-liquid interface to liquid-gas interface, with the TEA-hexane solution replaced by saturated TEA vapor. The dependence of product shape on precursor and catalyst concentrations can be explained by the competition between MOF formation and TEA diffusion into the precursor phase.</p> <p>The morphology, constitution and surface area of the MOF products were characterized by SEM, XRD and nitrogen adsorption testing, respectively. The particles were found to be exclusively MOF-5. The membranes were characterized as asymmetric. The top layer was particulate while the bottom layer had a sheet-like morphology. This was further revealed by XRD data as MOF-5 and MOF-2 (ZnBDC·DMF), respectively. This asymmetry was caused by a change of TEA diffusion rate during the synthesis process, which might result in a change in pH value for the membrane growth. Decent surface areas of the particles and membranes were measured.</p> <p>Apart from the free-standing membranes, MOF membranes on Anodisc support were also synthesized employing the same interfacial techniques. The MOF formation site, i.e. the interface, was confined to the upper end Anodisc pores and sealing the pores after the reaction. The difference in wetting force between DMF and hexane with Anodisc membrane material resulted in the difference of MOF layer morphology from liquid-liquid protocol and liquid-gas protocol. The later gave a continuous MOF membrane due to the absence of air bubble interference.</p> / Master of Science (MSc)

In this work the synthesis, characterization, and gas transport properties of hydrogen selective silica membranes were studied along with the catalytic reforming of CH₄ with CO₂ (CH₄ + CO z 2 CO + 2 H₂) in a hydrogen separation membrane reactor. The silica membranes were prepared by chemical vapor deposition (CVD) of a thin SiO₂ layer on porous supports (Vycor glass and alumina) using thermal decomposition of tetraethylorthosilicate (TEOS) in an inert atmosphere. These membranes displayed high hydrogen permeances (10⁻⁸ - 10⁷ mol m⁻² s⁻¹ Pa⁻¹) and excellent H₂ selectivities (above 99.9 %) over other gases (CH₄, CO, and CO₂). The membranes were characterized using Scanning Electron Microscopy and Atomic Force Microscopy, and the mechanism of gas transport was studied applying existing theories with a newly developed treatment. The catalytic reforming of CH₄ with CO₂ was carried out in a membrane reactor installed with a hydrogen separation ceramic membrane. The reaction was conducted at various pressures (1 - 20 atm) and temperatures (873 K and 923 K) at non-equilibrium conditions, and the results were compared with those obtained in a packed bed reactor in order to evaluate performance of the membrane reactor for the reaction. It was found that concurrent and selective removal of hydrogen from the reaction in the membrane reactor resulted in considerable enhancements in the yields of the reaction products, H₂ and CO. The enhancements in the product yields in the membrane reactor increased with pressure showing a maximum at 5 atm, and then decreased at higher pressures. This was due to a trade-off between a thermodynamic quantity (hydrogen production by the reaction) and transport property (hydrogen separation through the membrane). It was also found that the reverse water-gas shift (RWGS) reaction occurred simultaneously with the reforming reaction giving the detrimental effect on the reaction system by reducing the amount of hydrogen production in favor of water. This was particularly significant at high pressures. / Ph. D.

Sulfonated polysulfones BisAS and BPS were fabricated into dense polymer films, and their water and ion transport properties were systematically characterized. Fundamental NaCl and water transport properties were correlated with polymer chemistry, and water and NaCl permeability were found to increase with degree of sulfonation due to the increasing polymer water content. The BisAS backbone structure was found to result in greater water uptake, increasing water and salt permeability, though the polysulfones show evidence of sensitivity to the thermal casting process as well. Additionally, water and ion permeability and sorption values were determined for select polymers when exposed to a feed consisting of mixtures of monovalent and divalent cation salts. The divalent cations were found to sorb into the polymer much more favorably than the monovalent sodium, similarly to charged materials found in the literature. The sodium permeability of sulfonated polysulfones was found to increase in the presence of divalent cations by ratios of 2 to 5 times more than when exposed to an equivalent increase in feed charge concentration of monovalent cations. It has been hypothesized the more strongly charged divalent cations are neutralizing the sulfonate charges and suppressing Donnan exclusionary effects that reduce salt transport in charged polymers. / text

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