Access to clean water is one of the world's foremost challenges that has been addressed on a large scale by membrane-based separation processes for the last six decades. Commercial membrane technology within one operation, reverse osmosis, has remained consistent since the late 1970s, however within the last two decades, access to nanotechnology has created a realm of study involving thin film nanocomposite (TFN) membranes, in which nanoparticles are incorporated into existing membrane designs. Desirable properties of the nanoparticles may positively impact qualities of the membrane like performance, anti-fouling behavior, and physical strength. In the present work, two types of nanoparticles have been evaluated for their potential as TFN additives: cellulose nanocrystals (CNCs) and metal-organic framework (MOF) nanorods. CNCs were chosen due to their high aspect ratios, mechanical strength, and potential for surface functionalization. MOF nanorods are also of interest given their aspect ratios and potential for functionalization, but they also possess defined pores, the sizes of which may be tuned with post-synthetic modification. Both CNCs and MOF nanorods were incorporated into TFN membranes via interfacial polymerization, and the resulting membranes were characterized using a variety of techniques to establish their performances, but also to gain insight into how the presence of each nanoparticle might be affecting the membrane active layer formation. A resulting CNC membrane (0.5 wt% loading) exhibited a 160% increase in water flux and an improvement in salt rejection to 98.98 ± 0.41 % compared to 97.53 ± 0.31 % for a plain polyamide control membrane. Likewise, a MOF nanorod membrane (0.01 wt% loading) with a high ratio of acid chain modification exhibited a 95% flux increase with maintained high salt rejection. For the CNCs, the flux increase is attributed to the formation of nanoscale voids along the length of each particle that form during the interfacial polymerization. These nanochannels introduce new rapid water transport pathways within the active layer of each membrane while maintaining ion rejection. The proposed mechanism for the MOF nanorods also introduces nanochannels into each membrane, but the presence of each nanorod's pore structure may offer another transport pathway for water molecules, one that varies with pore size. In combination, these results have allowed the study of molecular transport of water molecules and various ion species within the active layer of a thin film composite RO membrane. Understanding these phenomena will allow the development of smarter membrane materials to address present-day and future separations challenges. Carbon nanotubes are also demonstrated as surface modifiers for forward osmosis (FO) membranes to address issues unique to the FO process, namely reverse solute flux (RSF). This method shows promise, as a coating density of 0.97 g/m2 reduced RSF for many draw solution species, including a 55% reduction for sodium chloride. / Doctor of Philosophy / Access to clean water is one of the world's foremost challenges that has been addressed on a large scale by membrane-based separation processes for the last six decades. Commercial membrane technology within one operation, reverse osmosis, has remained consistent since the late 1970s, however within the last two decades, access to nanotechnology has created a recent realm of study in which nanoparticles are incorporated into existing membrane designs. It is desired to use nanotechnology, or nanoparticles to improve membrane performance, i.e. create a membrane with better rejection of unwanted ions or contaminants or improve the amount of water that passes through the membrane. In the present work, two types of nanoparticles have been evaluated for their potential as TFN additives: cellulose nanocrystals (CNCs) and metal-organic framework (MOF) nanorods. Both CNCs and MOF nanorods were incorporated into membranes and the resulting membranes were characterized using a variety of techniques to establish how the nanoparticles affected performance. A resulting CNC membrane (0.5 wt% loading) exhibited a 160% increase in water flux (the amount of water passing through an area in a given amount of time) and an improvement in salt rejection. Likewise, a MOF nanorod membrane with a high ratio of acid chain modification exhibited a 95% flux increase with maintained high salt rejection. For both the CNCs and the MOFs, these performance changes are attributed to new pathways within each membrane for water flow that exist due to the presence of the nanoparticles in each system. In combination, these results have allowed the study of transport of water molecules and various ion species in each membrane. Understanding these results will allow the development of smarter membrane materials to address present-day and future separations challenges.

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Metal-Organic Frameworks (MOFs) are hybrid materials and are acknowledged as an important class of functional solid-state materials with high scientific interest in academia and industry alike. Their modular nature in terms of structural and compositional diversity, tunability, high surface area, and controlled pore size renders MOFs as the ideal candidate to address various persistent challenges pertaining to gas storage/separation, catalysis, drug delivery, and smart sensing. Through the field of reticular chemistry, targeted structures can be constructed through multiple design approaches, based on preselected building blocks prior to the assembly process. This thesis illustrates the merit of the supermolecular building layer (SBL) approach for the rational construction and discovery of highly connected and porous MOFs based on rare earth cations. Specifically, the emphasis of this study is on (i) the rational design and synthesis of 3-periodic MOFs based on SBLs pillared by ditopic ligands through post-synthetic modification (PSM) and in situ reactions. (ii) The investigation of the mixed-ligand system with different lengths and geometry of ditopic ligands on the isolation of metal clusters with distinct pore sizes. (iii) Gaining an overall insight into the exploration of different synthetic pathways that control the assembly of rare earth MOFs.

<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)

The threat of chemical warfare agent (CWA) attacks has persisted into the 21st century due to the actions of terror groups and rogue states. Traditional filtration strategies for soldier protection rely on high surface area activated carbon, but these materials merely trap CWAs through weak physisorption. Metal-organic frameworks (MOFs) have emerged as promising materials to catalyze the degradation of CWAs into significantly less toxic byproducts. The precise synthetic control over the porosity, defect density, and chemical functionality of MOFs offer exciting potential of for use in CWA degradation as well as a wide variety of other applications. Developing a molecular-level understanding of gas-MOF interactions can allow for the rational design of MOFs optimized for CWA degradation. Our research investigated the fundamental interfacial interactions between CWA simulant vapors, specifically sulfur mustard (HD) simulants, and zirconium-based MOFs (Zr-MOFs). Utilizing a custom-built ultrahigh vacuum chamber with infrared spectroscopic and mass spectrometric capabilities, the adsorption mechanism, diffusion energetics, and diffusion kinetics of HD simulants were determined. For 2-chloroethyl ethyl sulfide (2-CEES), a widely used HD simulant, infrared spectroscopy revealed that adsorption within Zr-MOFs primarily proceeded through hydrogen bond formation between 2-CEES and the bridging hydroxyls on the secondary building unit of the MOFs. Through the study of 1-chloropentane and diethyl sulfide adsorption, we determined that 2-CEES forms hydrogen bonds through its chlorine atom likely due to geometric constraints within the MOF pore environment. Temperature-programmed desorption experiments aimed at determining desorption energetics reveal that 2-CEES remain adsorbed within the pores of the MOFs until high temperatures, but traditional methods of TPD analysis fail to accurately measure both the enthalpic and entropic interactions of 2-CEES desorption from a single adsorption site. Infrared spectroscopy was able to measure the diffusion of adsorbates within MOFs by tracking the rate of decrease in overall adsorbate concentrations at several temperatures. The results indicate that 2-CEES diffusion through the pores of the MOFs is a slow, activated process that is affected by the size of the pore windows and presence of hydrogen bonding sites. We speculate that diffusion is the rate limiting step in the desorption of HD simulants through Zr-MOFs at lower temperatures. Stochastic simulations were performed in an attempt to deconvolute TPD data in order to extract desorption parameters. Finally, a combination of vacuum-based and ambient-pressure spectroscopic techniques were employed to study the reaction between 2-CEES and an amine-functionalized MOF, UiO-66-NH2. Although the presence of water adsorbed within UiO 66 NH2 under ambient conditions may assist in the reactive adsorption of 2-CEES, the reaction proceeded under anhydrous conditions. / Doctor of Philosophy / Chemical warfare agents (CWAs) are some of the most toxic chemicals on the planet and their continued use by terror groups and rogue nations threaten the lives of both civilians and the warfighter. Our work was motivated by a class of high surface area, highly porous materials that have shown the ability to degrade CWAs, specifically mustard gas, into less harmful byproducts. By determining the adsorption mechanism (how and where mustard gas “sticks” to the material), diffusion rates (how quickly mustard gas can travel through the pores of to reach the binding sites), and desorption energies (how strongly mustard gas “sticks” to the binding sites), we can alter the structure of these materials and to efficiently trap mustard gas and render it harmless. In the research described in this dissertation, we examined these fundamental interactions for a series of molecules that mimic the structure of mustard gas. and linear alkanes within several metal-organic frameworks with varying pore size. We observed the size of the pore environment affects the orientation that a given molecule sticks to binding sites as well as how quickly these compounds diffuse through the MOF. While the majority of these studies were conducted in a low-pressure environment that eliminated the presence of gas molecules in the atmosphere, research that exposed a MOF to a mustard gas mimic in an ambient environment demonstrated that gas molecules present in the atmosphere, especially water, can greatly impact the chemical interactions between mustard gas and zirconium-based MOFs.

The development of controllable drug delivery systems is crucial for reducing toxicity and minimizing off-target drug effects for patients undergoing chemotherapy. Metal–organic frameworks (MOFs) are a class of hybrid materials that have become of interest in the field of drug delivery. MOFs are composed of metal nodes and organic bridging ligands. MOFs have a wide range of desirable properties including chemical stability, high porosity, and structural tunability which have positioned them as successful drug carriers. Through judicious choice of linker, stimuli-responsive MOFs can be synthesized to achieve precise control over cargo release. Previously, our lab developed a novel light-responsive drug delivery system using a framework known as UiO-AZB (UiO= University of Oslo, AZB=4,4ʹ-azobenzenedicarboxylic acid). This MOF contains a photoswitchable azobenzene linker. Upon irradiation with ultraviolet light, the compound undergoes a structural change known as photoisomerization, resulting in degradation of the MOF structure and simultaneous release of encapsulated cargo. To improve the clinical relevance of our framework, we focus on developing synthetic methods for production of visible light-responsive azobenzene photoswitches. A green light-responsive MOF (UiO-AZB-F) containing a 4,4ʹ-(diazene-1,2- diyl)bis(3,5-difluorobenzoic acid) linker was developed as a drug delivery system for the treatment of colorectal cancer. Our work also focuses on optimizing various aspects of MOF design to maximize and diversify cargo loading and precisely control cargo release rates. A combined computational and experimental investigation of drug adsorption process reveals that the presence of solvent can significantly impact the adsorption of drug molecules within MOF pores. To address these concerns, a variety of drug loading procedures were screened to determine conditions for maximizing the loading of diverse drug cargoes. Conditions for the loading of single agents as well as chemotherapy cocktails were explored to expand the application of our delivery platform to other cancer types including lung, pancreatic, bladder and cervical. To modulate the release of cargo, a series of MOFs containing precise ratios of green light-responsive linker were synthesized to create a platform for sustained release. Remarkably, several MOF derivatives showed enhancement in drug adsorption, highlighting the important role of host–guest interactions in nanocarrier development. Holistically, this work highlights the promise of stimuli-responsive MOFs as drug delivery platforms. / Doctor of Philosophy / Cancer is one of the leading causes of death worldwide. In 2021, nearly 2 million people in the U.S. were diagnosed with cancer. For patients undergoing chemotherapy treatment, the side effects of potent chemotherapeutics are often debilitating. Drug- delivery systems serve as a promising platform for localizing the delivery of chemotherapeutic drugs within a diseased area. When chemotherapeutics are delivered precisely to tumor regions via drug delivery systems, systemic side effects are significantly diminished. In this work, a series of materials known as metal–organic frameworks (MOFs) are developed as carriers for chemotherapeutic cargo. Due to the incorporation of photoactivated compounds within the backbone, these MOFs can be degraded on-demand through green light irradiation. As the framework degrades into small molecule components, drug cargo is simultaneously released. Methods for maximizing MOF drug loadings, diversifying the types of cargo that can be incorporated, and modifying cargo release rates are also investigated. This work establishes stimuli-responsive MOFs as promising materials for on-demand drug delivery.

Increasing energy demand will not only aggravate global warming, but also cause fossil fuels shortage in the near future. Solar energy is an infinite green energy resource that can potentially satisfy our energy usage. By utilizing solar energy to drive reactions like water splitting, solar fuels system are able to produce valuable energy resource. Catalysts for water oxidation are the essential component of water splitting cells which have been intensively studied. As a solid state porous crystalline material with synthetic tunability, Metal-organic framework (MOF) is a promising platform for water oxidation catalysis due to its outstanding properties. Herein, we aimed to develop molecular catalysts incorporated MOF for water oxidation and study the reaction mechanism. Chapter 1 introduces the background of water oxidation and previous research on ruthenium nuclear water oxidation catalysts (WOCs). The reaction mechanism of binuclear and mononuclear ruthenium WOCs was briefly summarized. Opportunities for the design and the synthesis of MOF based WOCs were then discussed. Lastly, studies about MOF based WOCs were categorized based on the difference of the WOCs active site location in frameworks. Water oxidation catalyst [Ru(dcbpy)(tpy)OH2]2+ (RuTB) was incorporated into UiO-67 MOF (resulting materials denoted as RuTB-UiO-67) for chemical water oxidation in Chapter 2. Differences of catalytic reaction behavior between homogeneous RuTB and RuTB incorporated in MOF were examined. Based on MOF particle size dependent catalysis reaction experiments, in-MOF reactivity was anticipated to be primarily arose from redox hopping between RuTB active sites in the framework. In Chapter 3, RuTB-UiO-67 MOF thin films grown on conducting FTO substrate (RuTB-UiO-67/FTO) were synthesized to test their catalytic activity of electrochemical water oxidation. Electrochemical behavior of RuTB-UiO-67/FTO was found to be consistent with homogeneous RuTB by various electrochemistry study and in-situ X-ray absorption spectroscopy characterization. Scan-rate-dependent voltammetry study demonstrated the homogeneous distribution of electrochemical active sites throughout the MOF thin film. Diffusion controlled redox hopping was attributed to be the main charge transfer pathway during catalysis. In order to pursue photo-induced water splitting system, we further our study by investigating MOF based photoelectrochemical catalysis in Chapter 4. Photoelectrochemical alcohol oxidation was chosen as the preliminary-stage study towards the more challenging goal, photoelectrochemical water oxidation. Electron transfer processes of the photosensitizer ([Ru(bpy)2(dcbpy)]2+) and the catalyst (RuTB) doped UiO-67 MOF were investigated with transient absorption spectroscopy analysis. Finally, the role of redox hopping in electrocatalysis by MOF was reviewed in Chapter 5. Pathways of charge transfer in electroactive MOF were first summarized. Redox hopping in MOF was then compared with previous studies on redox active polymer thin films. Lastly, factors that will affect the rate of redox hopping of MOF electrocatalyst were discussed. / Doctor of Philosophy / Solar energy is the most abundant renewable energy resource that can satisfy our energy demand. Solar fuel devices like water splitting systems can generate hydrogen as an environmental friendly energy source. However, the commercialization of water splitting system was hindered by one particular half reaction, water oxidation. Therefore, the development of efficient and stable water oxidation catalysts is critical. Metal-organic framework (MOF) as a porous crystalline material with large surface area is a great platform for stable and reusable solid state water oxidation catalyst. Herein, we incorporated ruthenium based molecular water oxidation catalysts into a MOF denoted as UiO-67. The catalysts doped MOF was able to oxidize water chemically and electrochemically. Furthermore, light absorber molecules were introduced to the MOF to test their catalytic ability towards photoelectrochemical alcohol oxidation. It provides valuable information for the more challenging study of MOF based photoelectrochemcal water oxidation catalysts.