Luminescent metal organic frameworks (MOFs) are promising new materials with applications as sensors, photocatalysts, and other luminescent devices. Although MOFs retain the chemical and physical properties of their constituents, the properties of the MOF are often altered from those of its building blocks, making rational design and synthesis difficult. Anthracene is a polyaromatic hydrocarbon whose photophysical properties have been found to be easily tuned through structural modifications. The tunability of anthracene makes it an ideal candidate for use in luminescent devices, such as photoprobes and organic light emitting diodes. MOFs designed with π conjugated molecules like anthracene ligands possess similar photophysical properties such as absorption and fluorescence in the UV and visible spectrum. In hopes of better understanding how the photophysical properties of the organic ligand is altered upon incorporation into a MOF, the spectroscopic properties of anthracenedicarboxylic acids were studied before and after integration into zinc based MOFs. Steady state and time resolved measurements were performed on three anthracenedicarboxylic acids: 9,10-anthracenedicarboxylic acid, 2,6-anthracendicarboxylic acid, and 1,4-anthracenedicarboxylic acid. The position of the carboxylic acid groups on anthracene was found to effect the position and structure of the absorption and emission spectra. The difference in the spectra is attributed to the perturbation by the acid groups on certain electronic transitions with dipole moments across two of the three axes of anthracene. The position of the acid groups had different effects on the fluorescence quantum yields and lifetimes of the three anthracenic acids studied. Two of the linkers were synthesized into MOFs through a solvothermal reaction with zinc nitrate, to form PCN-13, from 9,10-anthracenedicarboxylic acid, and [Zn(C₁₆H₈O₄)(H₂O)]_n, from 2,6-anthracenedicarboxylic acid. The luminescent properties of the two MOFs were studied and compared to those of the free based linker. Incorporation of the luminescent anthracenedicarboxylic acids into Zn based MOFs were found to either increase or decrease the luminescent properties of the ligands. / Master of Science

Made available in DSpace on 2016-06-02T19:06:10Z (GMT). No. of bitstreams: 1 5674.pdf: 10691357 bytes, checksum: 01bd64a7f9ae5a29efe62ec0159122e0 (MD5) Previous issue date: 2013-10-31 / Financiadora de Estudos e Projetos / Frameworks are tools for software reuse that contribute for reducing costs and increased productivity in application development. Nowadays they are widely used and they tend to provide a satisfactory set of variabilities of a given domain. In general, a common trend in the evolution of these frameworks is the addition of new variabilities in attempting to address demands of a growing set of users. However, when such evolutions are not well designed and managed, the original architecture of the framework ends deviating from what had been previously planned, resulting in a complex and inflexible architecture. In addition, the new variabilities may belong to domains that were not originally planned for the framework, and become what we call Multiple Domains Frameworks (MDF). A problem of this kind of framework is that some variabilities may be useless for certain applications supported by the framework. Thus, MDF have problems for the Application Engineers (AE) and for Framework Engineers (FE). In the first case, the learning curve and the productivity are compromised, because AE will need to live together with a vast set of variabilities that may be unnecessary. For FE, the inflexibility of architecture complicates maintenance and composition/decomposition of smaller and more restrict versions of the framework. In this context, as an alternative to the aforementioned problems, we present an approach for modularization of MDFs into Framework Product Lines (FPL). An FPL is a product line in which the generated members are frameworks instead of applications. The main idea is that flexibility of this new architecture allows the generation of smaller and directed frameworks to the requirements of a domain/subdomain, avoiding the presence of features/variabilities that will never be used. One of the key points of this approach is to determine the Usage Scenario that the FPL must satisfy. Thus, an MDF can be decomposed in features with appropriate levels of granularity, a factor that directly impacts in the quality of an FPL. For the design of this approach, we conducted a case study in which the application framework GRENJ was modularized into an FPL. Two kinds of evaluation were performed. The first was an experiment to compare the effort to modularize a FMD in FPL using Aspect-Oriented Programming and Model-Driven Development. The second was a comparative study among applications developed with support of original framework and applications developed from the resulting FPL. The results show advantages in the reduction of efforts and increased productivity. / Frameworks são ferramentas de reuso que contribuem para a reducão de custos e aumento da produtividade no desenvolvimento de aplicações. Eles são amplamente empregados atualmente e tendem a fornecer um conjunto satisfatório de variabilidades de um determinado domínio. Em geral, uma característica comum no processo de evolução de frameworks e a adição de novas variabilidades na tentativa de atender demandas de um conjunto cada vez maior de usuários. Entretanto, quando tais evoluções não são bem planejadas e gerenciadas, a arquitetura original do framework acaba se desviando da que havia sido previamente planejada, resultando em uma arquitetura complexa e inflexível. Além disso, as novas variabilidades adicionadas podem pertencer a domínios que não foram originalmente planejadas para o framework; levando ao que chamamos de Frameworks de Multiplos Dominios (FMDs). Um problema desse tipo de framework e que determinadas variabilidades podem ser inúteis para certas aplicações apoiadas pelo framework. Dessa forma, FMDs apresentam problemas tanto para os engenheiros de aplicação (EA) quanto para os engenheiros do framework (EF). No primeiro caso, a curva de aprendizado e a produtividade são comprometidas, pois o EA precisara conviver com um conjunto grande de variabilidades que podem ser desnecessarias. Para os EFs, a inflexibilidade arquitetural acaba dificultando manutenções e a composição/decomposições de versões menores e mais restritas do framework. Nesse contexto, como uma alternativa para os problemas supracitados, apresenta-se neste trabalho uma abordagem para reestruturar FMDs em Linhas de Produtos de Frameworks (LPFs). Uma LPF e uma linha de produtos em que os membros gerados são frameworks ao invés de aplicações prontas. A ideia principal e que a flexibilidade dessa nova arquitetura permita a geração de frameworks menores e mais direcionados aos requisitos de um dominio/subdominio, evitando a presença de features/variabilidades que nunca serão usadas. Um dos pontos chave da abordagem proposta consiste em determinar o cenário de utilização que a LPF deve satisfazer. Assim, pode-se decompor um FMD em features com niveis adequados de granularidade, fator que impacta diretamente na qualidade da LPF. Para a concepção da abordagem conduziu-se um estudo de caso no qual o framework de aplicação GRENJ foi transformado em uma LPF. Foram realizados dois tipos de avaliação. O primeiro foi um experimento para comparar o esforço de remodularizar um FMD em LPF usando programação orientada a aspectos e desenvolvimento dirigido a modelos. O segundo foi um estudo que comparou aplicações desenvolvidas com o apoio do framework original com aplicações desenvolvidas a partir da LPF resultante. Os resultados apontaram vantagens com relação a redução dos esforços e aumento da produtividade.

Flexible electronics have garnered much interest over the past several decades. Hybrid organic-inorganic materials, such as metal-organic frameworks, offer a unique opportunity to encompass the effective electronic properties of the inorganic material and the flexible nature of the organic with the potential of enhancing other desirable properties, such as the contributing multiferroicity. Using a first principles approach, the goal of this thesis is to serve as a guide for identifying potential ferroelectric and multiferroic metal-organic frameworks. This is done through a screening method of metal-organic frameworks based on their geometry; certain symmetry operators cannot be present in a ferroelectric material. We report the theoretical spontaneous polarization for several dozens of MOFs in which ferroelectricity has not previously been tested, and further we discuss the likelihood that these materials could be engineered to have either increased polarization or added ferromagnetism, the latter of which would lead to multiferroicity.

A growing field of research has evolved around the design and synthesis of a variety of porous metal-organic framework (MOF) materials. Some of the most promising areas for which these materials are potentially useful candidates include gas-separation, heterogeneous catalysis, and gas-storage, and all of these applications involve placing the MOF under pressure. There is clearly a need to understand the structural response of MOFs to applied pressure. Nevertheless, hitherto there are very few published investigations dedicated to determining the behaviour of porous hybrid materials under pressure. Through the use of high-pressure single-crystal X-ray diffraction studies, a series of MOF materials have been studied. Here we present the effect of pressure on a series of MOFs. In chapter 2, the effect of pressure on the prototypical MOF called MOF-5 was studied experimentally from ambient pressure to 3.2 GPa. Here, application of pressure was driven by the hydrostatic medium being forced into the pores of the MOF, which altered the mechanical properties of MOF-5, in particular, medium inclusion delayed the onset of amorphization. Complementary computational analysis was also performed to elucidate further the effect of medium inclusion on compressive behaviour. Detailed structural data was also collected as a function of pressure on the MOF Cu-btc. Application of pressure caused solvent to be squeezed into the pores (like MOF-5) until a phase transition occurred, driven by the sudden compression and expansion of equatorial and axial Cu–O bonds. High-pressure post-synthetic modification of a MOF is reported for the first time. On application of pressure of 0.2 GPa to the Cu-based MOF called STAM-1, a ligand exchange reaction takes place resulting in a change in pore size, shape, and hydrophilicity of the resulting pores. Here, we also demonstrate the ability to force hydrophilic molecules into hydrophobic pores using pressure, counteracting the hydrophobic effect. A high-pressure combined experimental and computational study has been carried to probe the effect of pressure on ‘breathing’ mechanisms in a zeolitic imidazolate framework (or ZIF) called ZIF-8. The penetration of guest molecules and the accommodation of pressure are shown to be inextricably linked to the rotation of methylimidazolate groups in the structure. Finally, the application of pressure to the MOF Sc₂BDC₃ and the nitro functionalized derivative Sc₂(NO₂-BDC)₃ was also studied. Here, the effect of chemical modification of the organic ligand, whilst maintaining framework topology, has been investigated as it pertains to compressibility. Directionality of compression is observed and this is rationalized with respect to the framework topology and medium inclusion/exclusion.

Metal-organic frameworks (or coordination polymers) are a recently-identified class of porous polymeric materials, consisting of metal ions or clusters linked together by organic bridging ligands. The major advantage of MOFs over other traditional materials, such as zeolites or activated carbons, is that their synthesis methods have provided an extensive class of crystalline materials with high stability, tunable metrics, and organic functionality. The ability to modify the physical environment of the pores and cavities within MOFs allow tuning of the interactions with guest species, and serves as a route to tailor the chemical stability and/or reactivity of the frameworks for specific applications. The classical way to incorporate functional groups into a MOF is the modification of the organic precursor with specific substituents before synthesizing the MOF itself; we call this approach pre-functionalization method. Functionalization of organic precursors is the initial and necessary step to obtaining functionalized isostructural MOFs and also provides the possibility for the post-synthetic modification of MOFs. However, in some cases, the functional groups may interfere with MOF synthesis and alter the topology of desired MOF. The goal of this proposed research is to explore the possibilities of metal-organic frameworks (MOFs) as novel porous structures, to study the effect of functional groups on the topologies and adsorption behavior of MOFs, and to understand how the synthesis conditions affect the phase purity and the in-situ reaction of ligands.

Adsorption in porous materials plays a significant role in industrial separation processes. Here, the host-guest interaction and the pore shape influence the distribution of products. Metal-organic frameworks (MOFs) are promising materials for separation purposes as their diversity due to their building block synthesis from metal corners and organic linker gives rise to a wide range of porous structures. The selectivity differs from MOF to MOF as the size and shapes of their pores are tuneable by altering the organic linkers and thus changing the host-guest interactions in the pores. Using mainly molecular simulation techniques, this work focuses on three types of separations using MOFs. Firstly, the experimental incorporation of calix[4]arenes in MOFs as a linker to create additional adsorption sites is investigated. For a mixture of methane and hydrogen, it is shown that in the calix[4]arene-based MOFs, methane is adsorbed preferentially over hydrogen with much higher selectivities compared to other MOFs in the literature. Remarkably, it was shown that extra voids created by calix[4]arene-based linkers, were accessible to only hydrogen molecules. Secondly, the strong correlation between different pore sizes and shapes in MOFs and their capabilities to separate xylene isomers were investigated for a number of MOFs. Finally, the underlying molecular mechanism of enantioseparation behaviour in a homochiral MOF for a number of chiral diols is presented. The simulation results showed good agreement with experimental enantioselectivity values. It was observed that high enantioselectivity occurs only at high loadings and when a perfect match in terms of size and shape exists between the pore size and the adsorbates. Ultimately, the information obtained from molecular simulations will further our understanding of how network topology, pore size and shape in MOFs influence their performance as selective adsorbents for desired applications.

Thesis advisor: Chia-Kuang (Frank) Tsung / The core-shell hybrid structure is the simplest motif of two-component systems which consists of an inner core coated by an outer shell. Core-shell composite materials are attractive for their biomedical, electronic and catalytic applications in which interface between core and shell is critical for various functionalities. However, it is still challenging to study the exact role that interface plays during the formation of the core-shell structures and in the properties of the resulted materials. By studying the formation mechanism of a well interface controlled one-to-one metal nanoparticle (NP)@zeolite imidazolate framework-8 (ZIF-8) core-shell material, we found that the dissociation of capping agents on the NP surface results in direct contact between NP and ZIF-8, which is essential for the formation of core-shell structure. And the amount of capping agents on the NP surface has a significant effect to the crystallinity and stability of ZIF-8 coating shell. Guided by our understanding to the interface, one-to-one NP@UiO-66 core-shell structure has also been achieved for the first time. We believe that our research will help the development of rational design and synthesis of core-shell structures, particularly in those requiring good interface controls. / Thesis (MS) — Boston College, 2017. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.

This thesis explores the use of computational chemistry to aid in the design of metal-organic frameworks (MOFs) and other materials. A focus is placed on finding exceptional materials to be used for removing CO2 from fossil fuel burning power plants, with other avenues like vehicular methane storage and landfill gas separation being explored as well. These applications are under the umbrella of carbon capture and storage (CCS) which aims to reduce carbon emissions through selective sequestration. We utilize high-throughput screenings, as well as machine learning assisted discovery, to identify ideal candidate materials using a holistic approach instead of relying on conventional gas adsorption properties. The development of ideal materials for CCS requires all aspects of a material to be considered, which can be time-consuming. A large portion of this work has been with high-throughput, or machine learning assisted discovery of ideal candidates for CCS applications. The chapters of this thesis are connected by the goal of finding ideal materials for CCS. They are primarily arranged in increasing complexity of how this research can be done, from using high-throughput screenings with more simple metrics, up to multi-scale machine learning optimization of pressure swing adsorption systems. The work is not presented chronologically, but in a way to tell the best story. Work was done by first applying high-throughput computational screening on a set of experimentally realized MOFs for vehicular methane storage, post-combustion carbon capture, and landfill gas separation. Whenever possible, physically motivated figures of merits were used to give a better ranking and consideration of the materials. From this work, we were able to determine what the realistic limits might be for current MOFs. The work was continued by looking at carbon-based materials (primarily carbon nanoscrolls) for post-combustion carbon capture and vehicular methane storage. The carbon-based materials were found to outperform MOFs; however, further studies are needed to verify the results. Next, we looked at ways to improve the high-throughput screening methodology. One problem area was in the charge calculation, which could lead to unrealistic gas adsorption results. Using the split-charge equilibration method, we developed a robust way to calculate the partial atomic charges that were more accurate than its quick calculation counterparts. This led to gas adsorption properties which more closely mimicked the results determined from time-consuming quantum mechanically derived charges. Simplistic process optimization was then applied to nearly ~3500 experimental structures. To the best of our knowledge, this is the first time that any process optimization has been applied to more than 10s of materials for a study. The process optimization was done by evaluating the desorption at various pressures and choosing the value which gave the lowest energetic cost. It was found that a material synthesized by our collaborators, IISERP-MOF2, was the single best experimentally realized material for post-combustion carbon capture. What made this an interesting result is that by conventional metrics IISERP-MOF2 does not appear to be outstanding. Next, functionalized versions of MOFs were tested in a high-throughput manner, and some of those structures were found to outperform IISERP-MOF2. Although high-throughput computational screenings can be used to determine high-performance materials, it would be impossible to test all functionalized versions of some MOFs, let alone all MOFs. Functionalized MOFs are noteworthy because MOFs are highly tuneable through functionalization and can be made into ideal materials for a given application. We developed a genetic algorithm which, given a base structure and a target parameter, would be able to find the ideal functionalization to optimize the parameter while testing only a small fraction of all structures. In some cases, the CO2 adsorption was found to more than quadruple when functionalized. A better understanding of how materials perform in a PSA system was achieved by performing multi-scale optimizations. Experimentally realized MOFs were tested using atomistic simulations to derive gas adsorption properties. After passing through a few sensible filters, they were then screened using macro-scale pressure swing adsorption simulators, which model how gas separation may occur at a power plant. Using another genetic algorithm, the conditions that the pressure swing adsorption system runs at was optimized for over 200 materials. To the best of our knowledge, this is the highest amount of materials that have had been optimized for process conditions. IISERP-MOF2 was found to perform the best based on many relevant metrics, such as the energetic cost and how much CO2 was captured. It was also found that conventional metrics were unable to be used to predict a material’s pressure swing adsorption performance.

The advance in information technology has encouraged many countries to develop diverse methods of delivering information and communicating. The enhancement of Information and Communications Technology (ICT) has made it possible to deliver information and communication more rapidly and conveniently. Many emerging economies have taken advantage of ICT, including it in its development agenda. The development of ICT has had an impact on the provision of retail payment systems and its instruments. One of the main instruments, electronic money, promises to benefit the users with all the advantages of traditional notes and coins, and much more. Many countries have established or are considering the establishment of a regulatory framework of electronic money with its mass use in view. This volume examines the regulatory framework of electronic money, which some emerging economies have already established. It analyses the challenges faced in implementing laws and regulations for an evolving payment instrument where the regulatory framework may quickly become obsolete. The continuing development of electronic money with additional features and functions may invoke legislation leading to cross-regulatory functions among the authorities. The thesis is that the success of implementing the regulatory framework for electronic money will depend on the sound and effective coordination among relevant authorities. The role of the central bank and its relation to relevant authorities will be closely examined, because the central bank is often responsible for the development of payment systems, both wholesale and retail, especially in emerging economies, and plays a key role in its regulation. The use of a Memorandum of Understanding is proposed to ensure effective coordination and cooperation among relevant authorities. Malaysia will be used as the case study as the government has been enthusiastic in adopting electronic money, being involved in its development, implementation and regulation, which may not always be appropriate. Analysis in this thesis will be based on information as of 1 September 2004. The first three chapters of this volume will discuss the enhancement of ICT in emerging economies and the efforts taken to develop retail payment systems in consonant with ICT. Evaluation will be made on the relationship between ICT and the need to modernise the retail payment, which includes developing its regulatory framework. Analysis will then be made specifically on electronic money, focusing on stored-valued products. The overall development on stored-valued cards and why the acceptance of this product was initially slow will be examined, and then the underlying regulatory structure that may affect this is assessed. The last two chapters will focus on Malaysia. Analysis will be made on the approach taken in developing electronic money and its regulatory framework. The roles and functions of the relevant authorities involved will be critically examined, leading to a proposal to execute a Memorandum of Understanding among the authorities as a mechanism of ensuring the effective coordination and cooperation between the parties.

Made available in DSpace on 2019-03-29T23:56:52Z (GMT). No. of bitstreams: 0 Previous issue date: 2017-07-21 / Recently humanity has just crossed an important landmark in its history with the majority of people now living in large cities. This population concentration is capable of boosting the growth of positive indicators such as innovation, the production of new patents and supercreative employment, but increases the spread of diseases and the occurrence of crimes. Faced with the realization that crime rates grow year after year in these large urban centers, we sought to understand the dynamics of crime within cities. We investigate at the subscale of the neighborhoods of a highly populated city the incidence of property crimes in terms of both the resident and the floating population. Our results show that a relevant allometric relation could only be observed between property crimes and floating population. More precisely, the evidence of a superlinear behavior indicates that a disproportional number of property crimes occurs in regions where an increased flow of people takes place in the city. For comparison, we also found that the number of crimes of peace disturbance only correlates well, and in a superlinear fashion too, with the resident population. Our study raises the interesting possibility that the superlinearity observed in previous studies [Bettencourt et al., Proc. Natl. Acad. Sci. USA 104, 7301 (2007) and Melo et al., Sci. Rep. 4, 6239 (2014)] for homicides versus population at the city scale could have its origin in the fact that the floating population, and not the resident one, should be taken as the relevant variable determining the intrinsic microdynamical behavior of the system. This finding was the motivation for the codification of a framework that supports the analysis of population and crime data to propose city divisions that allow the allocation of police by floating population and resident population statistics. / Recentemente a humanidade atravessou um marco importante em sua história com a constatação de que a maioria da sua população agora se concentra nas grandes cidades. Essa concentração populacional é capaz de potencializar o crescimento de indicadores positivos como inovação, produção de novas patentes e empregos supercriativos, porém potencializa a propagação de doenças e a ocorrência de crimes. Diante da constatação de que as taxas de crimes crescem ano após ano em muitos desses grandes centros urbanos, buscou-se compreender a dinâmica do crime dentro de uma cidade. Foi investigada a incidência de crimes contra o patrimônio, tanto em função de população residente quanto em função de população flutuante, em aglomerados de população dentro de uma grande metrópole brasileira. Foi encontrada uma relevante relação alométrica, mas que só pôde ser observada entre o crimes contra o patrimônio e população flutuante. Mais precisamente, a evidência de um comportamento alométrico superlinear indica que um número desproporcional de crimes ocorre em regiões onde o fluxo de pessoas é maior. Também foi descoberto que o número de chamadas à polícia por perturbação de sossego alheio é correlacionado, também de forma superlinear, com a população residente. Esta tese levanta a interessante possibilidade de que a superlinearidade observada em estudos anteriores [Bettencourt et al., Proc. Natl. Acad. Sci. USA 104, 7301 (2007) e Melo et al., Sci. Rep. 4, 6239 (2014)] para crimes sérios em função de população, em escala de cidade, pode ter origem na mobilidade humana, e não na presença de residentes como se pensava. Esse achado foi a motivação para a codificação de um framework, que apoia a análise de dados de população e crime para que sejam propostas divisões de cidade que permitam a alocação de policiais por estatísticas de população flutuante e residente. Palavras-chave: Alometria, Crime, População