The adsorption isotherms can be used to study the properties of a sorbent and to determine the binding energy between a sorbent and a gas that is adsorbed on it. This study that was carried out on a metal organic framework called "Zeolitic imidazolate framework-8" (ZIF-8) as the sorbent. ZIF -8 is known to have a flexible structure and it has shown structural transformation during gas adsorption, at different temperatures. During this study, ZIF-8 was explored using Xenon adsorption. The range of temperatures for the Xenon adsorption isotherms was between 138 K and 157.56 K. During the adsorption of Xenon on ZIF -8 the lowest two isotherms (138 K and 140.39 K) showed two steps. The lower pressure step represents adsorption of Xenon on the "as - produced" ZIF-8. The extra step reflects the structural transition ("gate opening") that occurs due to the re-orientation of the organic linkers in ZIF-8. These changes increase the diameter of the apertures in the structure, and allow more gas molecules to enter in to the ZIF -8 structure. The Xenon adsorption isotherms were also used to determine the effective surface area of ZIF -8 by employing the "point B" method. The binding energy between Xenon and ZIF -8 was found using the isosteric heat for Xenon on ZIF-8 at low coverage. The kinetics of the Xenon adsorption was also studied during this experiment.

Rapid industrial globalization and technological development and energy consumption across the globe has significantly increased in response to mounting energy needs. The necessity for alternative and sustainable energy conversion devices has become apparent with the growth of energy utilization. In recent years, many research efforts have been made in the development of low-cost, efficient, environmentally friendly energy conversion devices. One type of energy conversion device, polymer electrolyte membrane fuel cells (PEMFCs), uses hydrogen oxidation at the anode and oxygen reduction at the cathode, with a solid-state proton conducting membrane between to generate energy with water as a by-product. PEMFCs use Nafion®, a sulfonated fluoropolymer-copolymer for proton transport; however, temperature restraints and the need for hydration limits the efficacy of this polymer. Moreover, the kinetics of oxygen reduction (ORR) are significantly slower at the cathode than the anode. Platinum is currently the industry standard, but these materials have limited resources, are expensive, and can be sensitive to carbon monoxide poisoning. Platinum is also the preferred catalyst for hydrogen evolution reactions (HER)—critical electrochemical reactions at the cathode for water splitting applications for the generation of hydrogen. Metal-Organic Frameworks (MOFs) have been explored for proton conductivity and as electrode catalysts. The tunability of metal ions and organic linkers both in situ and post-synthesis allows for the targeted design of specific surface areas and topologies while fine tuning selective functionality. Furthermore, due to morphology retention upon pyrolysis, MOFs are good platforms for logical design both pre- and post- carbonization. Taking advantage of the amendable design, along with tunable porosity and growth in controlled dimensions, this work explores the modification of a zinc based MOF as a possible candidate for proton conduction, as well modification of zinc, cobalt, and iron based MOFs for ORR catalysis. Post-synthetic modification was employed as a technique to oxidize the imidazolate ligand to include carboxylic acid functionality of a zinc based MOF. Proton conductivity generally arises from the mobility of the charge carriers present (i.e. carboxylates and phosphates). The incorporation of Brønsted acidity by way of free carboxylates is often challenging, as these are generally sites of coordination in the framework. Herein, we report the successful augmentation of Brønsted acidity with retention of framework crystallinity in a robust MOF. Additionally, the effects of metal content and carbonization temperature of MOFs were explored for ORR and HER. Cobalt and iron were doped either pre- or post-synthesis and carbonized in an inert atmosphere at various temperatures to generate MOF-derived carbons with catalytically active centers without the need for additional support. Carbons with parent MOFs containing moderate amounts of cobalt doping in a bimetallic Co/Zn MOF, or carbons that contained no zinc in the parent material, showed excellent electrocatalytic performance for ORR when carbonized at temperatures just at or above the boiling point of zinc. Zinc based MOFs were doped with various amounts of iron post-synthesis and prior to carbonization in an inert atmosphere. The formation of iron nanoflakes and nanorods on the surface of these carbons generated from the pyrolysis of these iron doped MOFs yielded high surface areas and outstanding electrochemical performance for ORR in both acidic and alkaline media. Likewise, excellent HER catalysis was exhibited by the MOF-derived carbon matrix with the highest iron loading pre-carbonization and more disperse nanorods. Not only does the amenability of MOFs make them a good platform for the direct inclusion of essential electrochemically active moieties, but it also allows for more targeted, nuanced, and rational design of materials needed to enhance proton conduction and electrochemical performance, particularly in cases on non-precious metal electrocatalysts where mechanisms are often not well-understood.

Thesis advisor: Chia-Kuang Tsung / Thesis advisor: Eranthie Weerapana / Metal-Organic Frameworks (MOFs) are crystalline porous materials constructed of metal ions and organic linkers, and have been widely utilized in gas storage, sensing, and chromatographic separation. The combination of MOF nanoparticles with other materials will broaden the utilization of MOF materials to a great extent. Several approaches for creating composites with the MOF, Zeolitic Imidazolate Framework-8 (ZIF-8), have been developed: dye and model drug molecules were encapsulated in ZIF-8 pores for potential drug delivery; mesoporous silica monolayer was epitaxially grown on the ZIF-8 surface for structural stability enhancement and hollow structure formation; UiO-66, another MOF subclass, was hierarchically encased inside ZIF-8 for double-phase gas separation and heterogeneous catalysis. By exploring the versatile ZIF-8 platform, these nanocomposites could have great applications in fields such as heterogeneous catalysis and drug delivery. / Thesis (MS) — Boston College, 2015. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.

Metal-organic frameworks (MOFs) are crystalline hybrid materials with interesting chemical and physical properties. This thesis is focused on the synthesis and characterization of different MOFs and their use in heterogeneous catalysis. Zeolitic imidazolate frameworks (ZIFs), including ZIF-4, ZIF -7 and ZIF -62, Ln(btc)(H2O) (Ln: Nd, Sm, Eu, Gd, Tb, Ho, Er and Yb), Ln2(bpydc)3(H2O)3, (Ln: Sm, Gd, Nd, Eu, Tb, Ho and Er), MOF-253-Ru and Zn(Co-salophen) MOFs were synthesized. Various characterization techniques were applied to study the properties of these MOFs. X-ray powder diffraction (XRPD), single crystal X-ray diffraction (XRD), scanning electron microscopy (SEM) and thermogravimetric analysis (TGA) were extensively used. The effect of synthesis parameters, such as batch composition and temperature, on the formation and morphology of ZIF-7 and ZIF-62 was studied. Structural transformation and flexibility of two series of lanthanide-based MOFs, Ln(btc)(H2O) (Ln: Nd, Ho and Er) and Ln2(bpydc)3(H2O)3, (Ln: Sm and Gd) upon drying and heating were characterized. Relations between metal coordination, structure flexibility and thermal stability among the Sm2(bpydc)3(H2O)3, Nd(btc)(H2O) and MOF-253 were investigated. Salophen- and phenanthroline-based organic linkers were designed, synthesized and characterized. Metal complexes were coordinated to these linkers to be used as catalytic sites within the MOFs. Catalytic studies using two MOF materials, Ln(btc) and MOF-253-Ru, as heterogeneous catalysts in organic transformation reactions were performed. The heterogeneous nature and recyclability of these MOFs were investigated and described. / <p>At the time of doctoral defence the following papers were unpublished and had a status as follows: Paper nr 4: Submitted; Paper nr 5: Submitted</p>

Propylene is one of the most important feedstocks of the petrochemical industry with an estimated 2015 worldwide demand of 100 million tons. Retrofitting conventional C3 splitters is highly desirable due to the huge amount of thermal energy required to separate propylene from propane. Membrane separation is among the alternatives that both academia and industry have actively studied during the past decades, however; many challenges remain to advance membrane separation as a scalable technology for energy-efficient propylene/propane separations. The overarching goal of this research is to provide a framework for development of scalable ZIF-based mixed-matrix membrane that is able to deliver attractive transport properties for advanced gas separations. Zeolitic imidazolate frameworks (ZIFs) were pursued instead of conventional molecular sieves (zeolites and carbon molecular sieves) to form mixed-matrix membrane due to their intrinsic compatibility with high Tg glassy polymers. A systematic study of adsorption and diffusion in zeolitic imidazolate framework-8 (ZIF-8) suggests that this material is remarkably kinetically selective for C3 and C4 hydrocarbons and therefore promising for membrane-based gas separation and adsorptive separation. As a result, ZIF-8 was used to form mixed-matrix dense film membranes with polyimide 6FDA-DAM at varied particle loadings and it was found that ZIF-8 significantly enhanced propylene/propane separation performance beyond the “permeability-selectivity” trade-off curve for polymeric materials. Eventually, this research advanced ZIF-based mixed-matrix membrane into a scalable technology by successfully forming high-loading dual-layer ZIF-8/6FDA-DAM asymmetric mixed-matrix hollow fiber membranes with attractive propylene/propane selectivity.

This thesis presents the synthesis, properties, and applications of two important classes of metal-organic frameworks (MOFs); lanthanide MOFs and hierarchical porous zeolitic imidazolate frameworks (ZIFs). The materials have been characterized using a wide range of techniques including diffraction, imaging, various spectroscopic techniques, gas sorption, dynamical light scattering (DLS) and thermogravimetric analysis (TGA). In Chapter 1, the unique features of MOFs and ZIFs as well as their potential applications are summarized. In Chapter 2, different characterization techniques are presented. Chapter 3 describes a family of new isoreticular lanthanide MOFs synthesized using tri-topic linkers of different sizes, H3L1-H3L4, denoted SUMOF-7I-IV (Ln) (SU; Stockholm University, Ln = La, Ce, Pr, Nd, Sm, Eu and Gd, Paper I). The SUMOF-7I-III (Ln) contain permanent pores and exhibit exceptionally high thermal and chemical stability. The luminescence properties of SUMOF-7IIs are reported (Paper II). The influences of Ln ions and the tri-topic linkers as well as solvent molecules on the luminescence properties are investigated. Furthermore, the potential of SUMOF-7II (La) for selective sensing of Fe (III) ions and the amino acid tryptophan is demonstrated (Paper III).  Chapter 4 presents a simple, fast and scalable approach for the synthesis of hierarchical porous zeolitic imidazolate framework ZIF-8 and ZIF-67 using triethylamine (TEA)-assisted approach (Paper IV). Organic dye molecules and proteins are encapsulated directly into the ZIFs using the one-pot method. The photophysical properties of the dyes are improved through the encapsulation into ZIF-8 nanoparticles (Paper IV). The porosity and surface area of the ZIF materials can be tuned using the different amounts of dye or TEA. To further simplify the synthesis of hierarchical porous ZIF-8, a template-free approach is presented using sodium hydroxide, which at low concentrations induces the formation of zinc hydroxide nitrate nanosheets that serve as in situ sacrificial templates (Chapter 5, Paper V). A 2D leaf-like ZIF (ZIF-L) is also obtained using the method. The hierarchical porous ZIF-8 and ZIF-L show good performance for CO2 sorption. / <p>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Manuscript. Paper 5: Manuscript.</p>

Anthropogenic emission of greenhouse gases has long been suspected to contribute to global warming and climate change. Most greenhouse gases are emitted in a mixture, so efficient methods and materials to separate and capture the gases are in demand in order to reduce emissions. A promising material group for this purpose is metal-organic frameworks (MOFs). This class of material have the ability to selectively adsorb green house gases due to its high porosity and high surface area. Zeolitic imidazolate frameworks (ZIFs) are a subclass of MOFs that are topologically similar to zeolites and are known for their good chemical and thermal stability.   The aim of this project was to investigate if the greenhouse gas (i.e. CO2 and SF6) capture performance of ZIFs could be improved and tuned using a mixed-linker approach with seven different imidazolate-based organic linkers of different sizes or with various functional groups. As well as to investigate the processability of MOFs using 3D printing. ZIFs composed of different ratios of 2-methylimidazolate as base linker and a second linker of imidazolate, benzimidazolate, 2-aminobenzimidazolate, 5,6-dimethylbenzimidazolate, and 4,5-dichloroimidazolate were succesfully made. The materials were all found to be crystalline, however, mixed-linker ZIFs containing 2-aminobenzimidazole, 5,6-dimethylbenzimidazole and dichloroimidazole were observed to contain more than a single phase. All samples showed to be somewhat porous towards CO2 and SF6, and there seem to be a trend where a low % of a bulkier linker (eg. bIm, ambIm) resulted in a higher uptake of SF6 whereas a high % resulted in a higher uptake of CO2. For dcIm it was the other way around, a low % showed a higher uptake for CO2  whereas a high % showed a higher uptake for SF6. For CO2, the ZIF containing 80% benzimidazolate showed the highest uptake of 9.81 wt%. For SF6, the 25% 4,5-dichloroimidazolate showed the highest uptake of 17.73 wt%. Furthermore, direct ink writing (DIW) 3D printing was also successfully utilized to process and structure a Mn-based MOF using carbopol as binder. The printed structure was found to have similar properties to the pristine MOF in regards to crystallinity and porosity.

In dieser Arbeit ein neues bioanalytisches Konzept untersucht, das nanoskalige Zeolith-Imidazolat-Frameworks (ZIFs) als Marker für antikörperbasierte Analysemethoden einsetzt, einschließlich Enzyme-Linked-Immunosorbent-Assay (ELISA) und Lateral Flow Immunoassay (LFIA). Der Vorteil von ZIFs als Marker gegenüber etablierten Materialien ist ihre vielseitige, einfache und kostengünstige Synthese. Dazu gehört die Möglichkeit, niedermolekulare Substanzen für zusätzliche Sensorzwecke zu verkapseln und für eine hohe Selektivität stabil an Biomakromoleküle zu konjugieren. Als modellhafter Zielanalyt von Relevanz wurden Phthalat-Acylester (PAEs) ausgewählt. Die Relevanz des Nachweises von PAEs ergibt sich aus ihren Eigenschaften als endokrin wirksame Chemikalien (EDCs) und krebserregend. In Kombination mit der Tatsache, dass PAEs aufgrund ihrer Verwendung als Weichmacher in Kindergeschirr, Spielzeug, Trinkflaschen und anderen Produkten auf Polyvinylchlorid-Basis in der Umwelt reichlich vorhanden sind, zeigt, wie wichtig der routinemäßige Nachweis von PAEs in Trinkwasser oder Lebensmitteln ist. / This work explores a new bioanalytical concept that employs nanosized Zeolite Imidazolate Frameworks (ZIFs) particles as labels for antibody-based analytical methods, including enzyme-linked immunosorbent assay (ELISA) and lateral flow immunoassay (LFIA). The advantage of ZIFs as labels over established materials is their versatile, facile, and cheap synthesis. This includes the ability to encapsulate low molecular weight substances for additional sensing purposes and for stable conjugation to biomacromolecules for high selectivity. As a model target analyte of relevance Phthalate acyl esters (PAEs) have been selected. The relevance of the detection of PAEs is due to their properties as endocrine disrupting chemicals (EDCs) and carcinogenic. Combined with PAEs being abundant on the environment because of their use as plasticizers in plastic-made tableware for children, toys, drinking bottles and other polyvinylchloride-based products, shows the importance or their routine detection of drinking water or foods being so critical.

Mixed matrix membranes (MMMs) have gained importance because they combine the desirable properties of the polymers and the organic/inorganic filler materials and they may have a very big potential. In this study polyethersulfone (PES) was used as polymeric material, and Zeolitic Imidazolate Framework-8 (ZIF-8) was used as porous filler material, and 2-hydroxy 5-methyl aniline(HMA), was used as a third component in membrane formulation. In this study, ZIF-8 crystals were synthesized with varying particle sizes, and a novel recycling methodology was developed to improve the efficiency of ZIF-8 production. ZIF-8 nano-crystals were synthesized by a 1-hour stirring method at room temperature and characterized by X-ray diffractometer, scanning electron microscopy (SEM), transmission electron microscopy (TEM), dynamic light scattering (DLS) and thermal gravimetric analysis (TGA). In order to investigate the effect of ZIF-8 loading on the membrane performance, different types of membranes were prepared with varying amounts of ZIF-8 between 10-60% (w/w). Moreover, ternary mixed matrix membranes were synthesized consisting of different amounts of ZIF-8 between 10-30% (w/w) and HMA 1-10% (w/w). Gas transport properties of the membranes were investigated by single gas permeation experiments of H2, CO2 and CH4 at 3 bar feed pressure. In order to investigate the effect of feed pressure on the gas transport properties of the membranes, single gas experiments were conducted on 3, 6, 8, 10 and 12 bar feed pressures. Moreover, binary gas permeation experiments of CO2/CH4 pair were conducted through selected membranes at 3 bar and 12 bar feed pressures. In addition to gas permeation experiments, the morphology and thermal characteristics of the membranes were characterized by SEM, TGA and differential scanning calorimetry (DSC) analysis. The incorporation of ZIF-8 crystals into continuous PES matrix resulted in high performance gas separation membranes. The permeabilities of all studied gases increased with ZIF-8 loading while the ideal selectivities showed a slight decrease compared to neat PES membrane. Highly reproducible and repeatable results were obtained up to 30 % w/w ZIF-8 loading, while membrane formulation reproducibility was decreased for higher ZIF-8 contents (&gt / 30 w/w %). Addition of HMA improved the gas separation performances of the binary membranes significantly by decreasing permeabilities and increasing ideal selectivities. PES/ZIF-8(%20)/HMA(%7) membrane has the best separation performance for all gases among the ternary membranes. When 7 w/w % HMA was added to PES/ZIF-8(%20) membrane, H2 permeability decreased from 26.3 to 13.7 barrer, while H2/CH4 ideal selectivity increased from 61.8 to 103.7. Increasing feed pressures appreciably increased the separation performances of all membranes. While the H2 permeability is pressure independent, the CO2 and CH4 permeabilities were reduced with increasing feed pressures and the highest selectivity improvement was observed in H2/CH4 pair for all membrane compositions. For instance, when the feed pressure was increased from 3 bar to 12 bar, the percentage improvements in ideal selectivities through PES/ZIF-8(%10)/HMA(%4) membrane were calculated as 26, 69, 113 % for the H2/CO2, CO2/CH4 and H2/CH4 gas pairs / respectively. This results show that working at higher feed pressures will be more advantageous for separation of the studied gas pairs. The ideal selectivities and the separation factors were equal to each other for all membrane compositions both for 3 and 12 bar operating pressures.

Distillation and absorption columns offer significant energy demands for future development in the petrochemical and fine chemical industries. Membranes and adsorbents are attractive alternatives to these classical separation units due to lower operating cost and easy device fabrication; however, membranes possess an upper limit in separation performance that results in a trade-off between selectivity (purity) and permeability (productivity) for the target gas product, and adsorbents require the need to be water-resistant to natural gas streams in order to withstand typical gas compositions. Composite membranes, or mixed-matrix membranes, are an appealing alternative to pure polymeric membrane materials by use of a molecular sieve “filler” phase which has higher separation performance than the pure polymer. In this thesis, the structure-property-processing relationships for a new class of molecular sieves known as zeolitic imidazolate frameworks (ZIFs) are investigated for their use as the filler phase in composite membranes or as adsorbents. These materials show robust chemical and thermal stability and are a promising class of molecular sieves for acid gas (CO₂/CH₄) separations. The synthesis of mixed-linker ZIFs is first investigated. It is shown that the organic linker composition in these materials is controllable without changing the crystal structure or significantly altering the thermal decomposition properties. There are observable changes in the adsorption properties, determined by nitrogen physisorption, that depend on the overall linker composition. The results suggest the proposed synthesis route facilitates a tunable process to control either the adsorption or diffusion properties depending on the linker composition. The structure-property-processing relationship for a specific ZIF, ZIF-8, is then investigated to determine the proper processing conditions necessary for fabricating defect-free composite membranes. The effect of ultrasonication shows an unexpected coarsening of ZIF-8 nanoparticles that grow with increased sonication time, but the structural integrity is shown to be maintained after sonication by using X-ray diffraction, Pair Distribution Function analysis, and nitrogen physisorption. The permeation properties of composite membranes revealed that intense ultrasonication is necessary to fabricate defect-free membranes for CO₂/CH₄ gas separations. Finally, the separation properties of mixed-linker ZIFs is investigated by using adsorption studies of CO₂ and CH₄ and using composite membranes with differing linker compositions. Adsorption properties of mixed-linker ZIFs reveal that these materials possess tunable surface properties, and a selectivity enhancement of six fold over ZIF-8 is observed with mixed-linker ZIFs without changing the crystal structure. Gas permeation studies of composite membranes reveal that the separation properties of mixed-linker ZIFs are different from their parent frameworks. By proper selection of mixed-linker ZIFs, there is an overall improvement of separation properties in the composite membranes when compared to ZIF-8.