Global warming along with the climate change derived from the World's demand for energy are among the greatest challenges to our society. To tackle climate change issue, research must focus on proposing practical approaches for carbon emissions reduction and environmental remediation. This thesis focuses on carbon dioxide separation mainly from flue gases (major sources of carbon dioxide emissions) using metal organic frameworks (MOFs) to reduce its impact on the global warming hence the climate change. MOFs are a class of crystalline porous adsorbents with structures that attract CO2 selectively and store it in their porous frameworks. Over the course of this PhD research, the fundamental aspects of these materials, as well as their practical applications, have been investigated. For example, the synthesis recipe of copper (II) benzene-1,3,5-tricarboxylate (CuBTC) MOF was improved to deliver a product of high yield ( > 89%) and free of by-product. Also, a mechanism study on the hydrothermal stability CuBTC MOF was carried out under simulated flue gas conditions and delivered the first experimental proof of the decomposition mechanism of CuBTC MOF caused by the water vapour. The fundamental understanding of the stability of materials then motivated the research into the development of a facile method of using an economic functional dopant (i.e. glycine) to strengthen the structure of CuBTC MOF (completely stable towards water vapour), as well as to improve the selectivity of resulting materials to CO2 (by 15% in comparison to the original CuBTC MOF). The suitability of the CuBTC MOF for fixed bed adsorption processes was also assessed using a combined experimental and process simulation method. In addition to the experimental approaches, molecular simulation based on grand canonical Monte Carlo method was also used to understand the effect of structural defects of MOFs on the CO2 adsorption isotherms.

Third phase formation is an undesirable phenomenon during the PUREX process, which is a continuous liquid-liquid extraction approach for the reprocessing of uranium and plutonium from spent nuclear fuel. When third phase formation occurs, the organic extraction solution splits into two layers. The light upper layer, which is commonly named the light organic phase, contains a lower concentration of metal ions, tri-n-butyl phosphate (TBP) and nitric acids but is rich in the organic diluent. The heavy lower layer, which is commonly named the third phase, contains high concentrations of metal ions, TBP and nitric acids. As the third phase contains high concentrations of the uranium and plutonium complexes it can thus cause processing and safety concerns. Therefore, a comprehensive understanding of the mechanism of third phase formation is needed so as to improve the PUREX flowsheet. To investigate third phase formation through molecular simulations, one should first obtain reliable molecular models. A refined model for TBP, which uses a new set of partial charges generated from our density functional theory calculations, was proposed in this study. To compare its performance with other available TBP models, molecular dynamics simulations were conducted to calculate the thermodynamic properties, transport properties and the microscopic structures of liquid TBP, TBP/water mixtures and TBP/n-alkane mixtures. To our knowledge, it is only TBP model that has been validated to show a good prediction of the microscopic structure of systems that consist of both hydrophobic and hydrophilic species. This thesis also presents evidence that the light-organic/third phase transition in the TBP/n-dodecane/HNO3/H2O systems, which is relevant to the PUREX process, is an unusual transition between two isotropic, bi-continuous micro-emulsion phases. The light-organic /third phase coexistence was first observed using Gibbs Ensemble Monte Carlo (GEMC) simulations and then validated through Gibbs free energy calculations. Snapshots from the simulations as well as the cluster analysis of the light organic and third phases reveal structures akin to bi-continuous micro-emulsion phases, where the polar species reside within a mesh whose surface consists of amphiphilic TBP molecules. The non-polar n-dodecane molecules are outside this mesh. The large-scale structural differences between the two phases lie solely in the dimensions of the mesh. To our knowledge, the observation of the light-organic/third phase coexistence through simulation approaches and a phase transition of this nature have not previously been reported. Finally, this thesis presents evidence that the microscopic structure of the light organic phase of the Zr(IV)/TBP/n-octane/HNO3/H2O system, which is also related to the PUREX process, is different from that of the common hypothesis, where such system is consisted of large ellipsoidal reverse micelles. Snapshots from simulations, hydrogen bonding analysis and cluster analysis showed that the Zr4+, nitrate, TBP and H2O form extended aggregated networks. Thus, as above, we observe a bi-continuous structure but this time with embedded local clusters centred around the Zr4+ ions. The local clusters were found to consist primarily of Zr(NO3)4·3TBP complexes. This finding provides a new view of the structure of the Zr(IV)/TBP/n-octane/HNO3/H2O system.

Antibody microarrays constitute a next-generation sensing platform that has the potential to revolutionize the way that molecular detection is conducted in many scientific fields. Unfortunately, current technologies have not found mainstream use because of reliability problems that undermine trust in their results. Although several factors are involved, it is believed that undesirable protein interactions with the array surface are a fundamental source of problems where little detail about the molecular-level biophysics are known. A better understanding of antibody stability and antibody-antigen binding on the array surface is needed to improve microarray technology. Despite the availability of many laboratory methods for studying protein stability and binding, these methods either do not work when the protein is attached to a surface or they do not provide the atomistic structural information that is needed to better understand protein behavior on the surface. As a result, molecular simulation has emerged as the primary method for studying proteins on surfaces because it can provide metrics and views of atomistic structures and molecular motion. Using an advanced, coarse-grain, protein-surface model this study investigated how antibodies react to and function on different types of surfaces. Three topics were addressed: (1) the stability of individual antibodies on surfaces, (2) antibody binding to small antigens while on a surface, and (3) antibody binding to large antigens while on a surface. The results indicate that immobilizing antibodies or antibody fragments in an upright orientation on a hydrophilic surface can provide the molecules with thermal stability similar to their native aqueous stability, enhance antigen binding strength, and minimize the entropic cost of binding. Furthermore, the results indicate that it is more difficult for large antigens to approach the surface than small antigens, that multiple binding sites can aid antigen binding, and that antigen flexiblity simultaneously helps and hinders the binding process as it approaches the surface. The results provide hope that next-generation microarrays and other devices decorated with proteins can be improved through rational design.

Metal-organic frameworks (MOFs) are a new class of nanoporous materials that have received great interest since they were first synthesized in the late 1990s. Practical applications of MOFs are continuously being discovered as a better understanding of the properties of materials adsorbed within the nanopores of MOFs emerges. One such potential application is as a component of an explosive-sensing system. Another potential application is for hydrogen storage. This work is focused on tailoring MOFs to adsorb/desorb the explosive, RDX. Classical grand canonical Monte Carlo (GCMC) and molecular dynamic (MD) simulations have been performed to calculate adsorption isotherms and self-diffusivities of RDX in several IRMOFs. Because gathering experimental data on explosive compounds is dangerous, data is limited. Simulation can in part fill the gap of missing information. Through these simulations, many of the key issues associated with MOFs preconcentrating RDX have been resolved. The issues include both theoretical issues associated with the computational generation of properties and practical issues associated with the use of MOFs in explosive-sensing system. Theoretically, we evaluate the method for generating partial charges for MOFs and the impact of this choice on the adsorption isotherm and diffusivity. Practically, we show that the tailoring of an MOF with a polar group like an amine can lead to an adsorbent that (i) concentrates RDX from the bulk by as much as a factor of 3000, (ii) is highly selective for RDX, and (iii) retains sufficient RDX mobility allowing for rapid, real time sensing. Many of the impediments to the effective explosive detection can be framed as shortcomings in the understanding of molecule surface interactions. A fundamental, molecular-level understanding of the interaction between explosives and functionalized MOFs would provide the necessary guidance that allows the next generation of sensors to be developed. This is one of the main driving forces behind this dissertation. Another important achievement in this work is the demonstration of a new direction for tailoring MOFs. A new class of tailored MOFs containing porphyrins has been proposed. These tailored MOFs show greater capability for hydrogen storage, which also demonstrated the great functionalization of MOFs and great potential to serve as preconcentrators. The use of a novel multiscale modeling technique to develop equations of state for inhomogeneous fluids is included as a supplement to this dissertation.

Metal-Organic Frameworks (MOFs) are three-dimensional porous nanomaterials with a variety of applications, including catalysis, gas storage and separation, and sustainable energy. Their potential as air filtration systems is of interest for designer carbon capture materials. The chemical constituents (i.e. organic ligands) can be functionalized to create rationally designed CO2 sequestration platforms, for example. Hardware and software alike at the bleeding edge of supercomputing are utilized for designing first principles-based molecular models for the simulation of gas sorption in these frameworks. The classical potentials developed herein are named PHAST -- Potentials with High Accuracy, Speed, and Transferability, and thus are designed via a "bottom-up" approach. Specifically, models for N2 and CH4 are constructed and presented. Extensive verification and validation leads to insights and range of applicability. Through this experience, the PHAST models are improved upon further to be more applicable in heterogeneous environments. Given this, the models are applied to reproducing high level ab initio energies for gas sorption trajectories of helium atoms in a variety of rare-gas clusters, the geometries of which being representative of sorption-like environments commonly encountered in a porous nanomaterial. This work seeks to push forward the state of classical and first principles materials modeling. Additionally, the characterization of a new type of tunable radical metal--carbene is presented. Here, a cobalt(II)--porphyrin complex, [Co(Por)], was investigated to understand its role as an effective catalyst in stereoselective cyclopropanation of a diazoacetate reagent. Density functional theory along with natural bond order analysis and charge decomposition analysis gave insight into the electronics of the catalytic intermediate. The bonding pattern unveiled a new class of radical metal--carbene complex, with a doublet cobalt into which a triplet carbene sigma donates, and subsequent back-bonding occurs into a pi* antibonding orbital. This is a different type of interaction not seen in the three existing classes of metal-carbene complexes, namely Fischer, Schrock, and Grubbs. Finally, the virtual engineering of enhanced chemical warfare agent (CWA) detection systems is discussed. As part of a U.S. Department of Defense supported research project, in silico chemical modifications to a previously synthesized zinc-porphyrin, ZnCS1, were made to attempt to achieve preferential binding of the nerve agent sarin versus its simulant, DIMP (diisopropyl methylphosphonate). Upon modification, a combination of steric effects and induced hydrogen bonding allowed for the selective binding of sarin. The success of this work demonstrates the role that high performance computing can play in national security research, without the associated costs and high security required for experimentation.

In the current context of rapidly depleting petroleum resources and growing environmental concerns, it is important to develop materials to harvest and store energy from renewable and sustainable sources. Hydrogen has the potential to be an alternative energy source, since it has higher energy content than petroleum. However, since hydrogen has very low volumetric energy density, hence it is important to design nano porous materials which can efficiently store large volumes of hydrogen gas by adsorption. In this regard carbon nanotube and Metal Organic Framework (MOFs) based materials are worth studying. Ionic liquids (IL) are potential electrolytes that can improve energy storage capacity and safety in Li ion batteries. Therefore it is important to understand IL's thermodynamic and transport properties, especially when it is in contact with electrode surface and mixed with Li salt, as happens in the battery application. This dissertation presents computation and simulation based studies on: 1. Hydrogen storage in carbon nanotube scaffold. 2. Mechanical property and stability of various nanoporous Metal Organic Frameworks. 3. Thermodynamic and transport properties of [BMIM][BF4] ionic liquid in bulk, in Li Salt mixture, on graphite surface and under nanoconfinement. In the first study, we report the effects of carbon nanotube diameter, tube chirality, tube spacer distance, tube functionalization and presence of Li on hydrogen sorption capacity and thermodynamics at different temperature and pressure. In the second one, we observe high pressure induced structural transformation of 6 isoreticular MOFs: IRMOF-1. IRMOF-3, IRMOF-6, IRMOF-8, IRMOF-10 and IRMOF-14, explore the deformation mechanism and effect of Hydrogen inside crystal lattice. In the third study, we observe the equilibrium thermodynamic and transport properties of [BMIM][BF4] ionic liquid. The temperature dependence of ion diffusion, conductivity, dielectric constant, dipole relaxation time and viscosity have been observed and found similar behavior to those of supercooled liquid. The ion diffusion on graphite surfaces and under nanoconfinement was found to be higher compared to those in bulk.

One of the most important challenges in low-temperature fuel cell technology is improving the catalytic efficiency at the electrode-catalyst where the oxygen reduction reaction (ORR) occurs. Platinum is the best pure catalyst for this reaction but its high cost and scarcity hinder the commercial implementation of fuel cells in automobiles. Pt-based alloys are promising alternatives to substitute platinum while maintaining the efficiency and life-time of the pure catalyst. However, the acid medium and the oxidation of the surface reduce the activity and durability of the alloy catalyst through changes in its local composition and structure. Molecular simulation techniques are applied to characterize the thermodynamics and dynamic evolution of the surface of platinum-based alloy catalysts under reaction conditions.1-10 A simulation scheme of the surface oxidation is proposed which combines classical molecular dynamics (MD) and density functional theory (DFT). This approach is able to reproduce the main features of the oxidation phenomena observed experimentally, it is concluded that the dissolution mechanism of metal atoms involves: 1) Surface segregation of alloy atoms, 2) oxygen absorption into the subsurface of the catalyst, and 3) metal detachment through the interaction with ions in the solvent. Therefore, to improve the durability of platinum-based alloy catalysts, the steps of the dissolution mechanism must be prevented. A versatile 3-D kinetic Monte Carlo (KMC) code is developed to study the degradation and dealloying in nanocatalysts. The results on the degradation of Pt nanoparticles under different potential regimes demonstrate that the dissolution depends on the potential path to which the nanocatalyst is exposed. Metal atoms detach from the boundaries of (111) facets expecting a reduction in the activity of the nanoparticle. Also, the formation of Pt hollow nanoparticles by the Kirkendall effect is addressed, the role of vacancies is crucial in the removal of the non-noble core that yields to hollow nanoparticles. To investigate the reasons for the experimentally found enhanced ORR activity in porous/hollow nanoparticles, the effect of subsurface vacancies on the main ORR activity descriptors is studied with DFT. It is found that an optimum amount of vacancies may enhance the ORR activity of Pt-monolayer catalysts over certain alloy cores by changing the binding energies of O and OH.

Le procédé de granulation en voie humide nécessite l'ajout d'un agent d’enrobage ou liant, typiquement composé d'agents tensioactifs, d'eau, de plastifiant et de charge hydrophobe. Cependant, dans les procédés de granulation en voie sèche, l'agent d’enrobage est ajouté sous la forme de fines particules solides. L’objectif de ce travail est double : d’une part, examiner le comportement des particules dans les systèmes secs et aqueux aux échelles microscopique et mésoscopique, et d’autre part, développer des méthodologies prédictives permettant de choisir le liant adéquat et formuler la bonne solution d’enrobage. Dans le cadre de cette étude, nous avons utilisées l'hydroxypropyl-méthylcellulose (HPMC) et la cellulose d'éthyle (EC) comme agents d’enrobage, polyvinylpyrrolidone (PVP) et la cellulose microcristalline (MCC) généralement utilisés comme liants, l'acide stéarique (SA) qui est une charge hydrophobe, et le polyéthylène glycol (PEG) comme plastifiant. Tous ces matériaux sont largement utilisés dans les industries alimentaires et pharmaceutiques. La réussite d’une granulation dépend de l’affinité entre les particules primaires et le liant. Afin de prédire l'affinité liant-substrat en milieu sec et en milieu aqueux, nous avons comparé deux approches; la première est basée sur le travail de l'adhésion alors que la seconde s’appuie sur le concept de résistance à la traction idéale. L’équation de résistance à la traction idéale a été étendue aux systèmes ternaires dans le but de l’appliquer pour la granulation en milieu aqueux. Les approches développées ont été ensuite confrontées aux données expérimentales sur différent systèmes (composées de PVP, MCC, HPMC, SA, EC, PEG et l'eau). Nous avons ainsi trouvé que l’approche basée sur le travail d'adhésion semble donner de meilleures prédictions des affinités. Les deux approches prédisent que le HPMC est un bon liant pour le MCC. Les résultats indiquent également que le PEG a une bonne affinité avec le HPMC et le SA. Nous avons ensuite étudié la structure des agglomérats formés dans les formulations colloïdales utilisées dans les procédés d’enrobage. Pour ce faire, nous nous sommes appuyés sur des analyses expérimentales et des simulations mésoscopiques. Ces dernières reposent sur l’utilisation de la méthode de dynamique des particules dissipatives (DPD) dans laquelle les composés sont décrits comme un ensemble de billes souples (approche « coarse-grain ») interagissant selon le modèle de Flory-Huggins. Les interactions répulsives entre les billes ont été évaluées en utilisant le paramètre de solubilité (δ) calculé par simulation moléculaire tout-atome. Les résultats de simulation DPD ont été comparés aux résultats expérimentaux obtenus par plusieurs voies : cryogénique-MEB, analyse de distribution de taille de particule et par la technique DSC. Les résultats de la simulation DPD montrent que le polymère HPMC est un meilleur agent stabilisant pour le SA que le PVP et le MCC. En outre, HPMC est capable de recouvrir la particule de SA d'une couche épaisse et d’y pénétrer en profondeur, empêchant ainsi l’agglomération et la croissance des cristaux de SA. Néanmoins, HPMC est incapable de stabiliser les particules de SA lorsque celles-ci sont en quantités élevées (supérieurs à 10% (w/w)). Nous constatons également que le PEG se diffuse à l'intérieur des chaînes de HPMC entrainant l’extension de ce dernier, formant ainsi un polymère composite lisse. Les résultats expérimentaux montrent des tendances similaires; l’analyse de la distribution de taille de particule indique qu’en présence de HPMC, pour de faible pourcentages de SA (au-dessous de 10% (w/w)), la majorité des particules de SA sont inférieures à 1 μm de diamètre. Les images MEB révèlent que HPMC entoure les cristaux de SA avec un film texturé et ancre sur leur surface. / Wet granulation process requires the addition of a coating agent or binder, typically composed of surfactants, water, plasticizers and fillers. In dry granulation however, the coating agent is added to the system in the form of fine solid particles. Our goals are to investigate the particles behaviour and agglomeration mechanism in dry and aqueous systems at the micro and meso scales, and also, to develop predictive methodologies and theoretical tools of investigation allowing to choose the adequate binder and to formulate the right coating solution. In this study we chose materials widely used in food and pharmaceutical industries, including; coating agents such as Hydroxypropyl-methylcellulose (HPMC) and Ethyl cellulose (EC), binders such as Polyvinylpyrrolidone (PVP) and Microcrystalline cellulose (MCC), hydrophobic filler such as Stearic acid (SA) and plasticizer such as Polyethylene glycol (PEG). A successful granulation requires good affinity between host and guest particles. In this context, in the first part of this work, two approaches to predict the binder-substrate affinity in dry and in aqueous media were compared; one based on the work of adhesion and the other based on the ideal tensile strength. The concept of ideal tensile strength was extended to ternary systems and applied for granulation in aqueous media. The developed approaches were thereafter tested for various systems (composed of PVP, MCC, HPMC, SA, EC, PEG and water) and compared to experimental observations. Approaches yielded results in good agreement with the experimental observations, but the work of adhesion approach might give more accurate affinity predictions on the particles affinity than the ideal tensile strength approach. Both approaches predicted that HPMC is a good binder for MCC. Results also indicated that PEG has a good affinity with HPMC and SA. In a second part of our work, we used mesoscale simulations and experimental techniques to investigate the structure of agglomerates formed in aqueous colloidal formulations used in coating and granulation processes. For the simulations, dissipative particle dynamics (DPD) and a coarse-grained approach were used. In the DPD method, the compounds were described as a set of soft beads interacting according to the Flory-Huggins model. The repulsive interactions between the beads were evaluated using the solubility parameter (δ) as input, where, δ was calculated by all-atom molecular simulations. The mesoscale simulation results were compared to experimental results obtained by Cryogenic-SEM, particle size distribution analysis and DSC technique. According to the DPD simulations, HPMC polymer is a better stabilizing agent for SA than PVP and MCC. In addition, HPMC is able to cover the SA particle with a thick layer ant to adsorb in depth into its inner core, preventing SA agglomeration and crystal growth. But, for high amounts of SA (above 10% (w/w)), HPMC is unable to fully stabilize SA. We also found that PEG polymer diffuses inside HPMC chains thereby extending and softening the composite polymer. Experimental results presented similar trends; particle size distribution analysis showed that in the presence of HPMC, for low percentages of SA (below 10% (w/w)), the majority of SA particles are below 1 μm in diameter. SEM images revealed that HPMC surrounds SA crystals with a hatching textured film and anchors on their surface.

CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel Superior / A separaÃÃo de CO2 a partir de misturas gasosas industriais consiste em um importante tema tanto do ponto de vista cientÃfico quanto ambiental. O interesse suscitado pelo tema està diretamente relacionado à problemÃtica da presenÃa do diÃxido de carbono tanto nos gases de combustÃo (flue gas) quanto no gÃs natural (GN) e biogÃs. A absorÃÃo usando aminas à uma tecnologia madura que tem sido utilizado na indÃstria do gÃs natural para remoÃÃo de CO2. No entanto, apresenta algumas desvantagens, tais como corrosÃo dos equipamentos e alto consumo de energia para regenerar o absorvente. LÃquidos iÃnicos (LIs) tÃm sido propostos como uma alternativa aos solventes orgÃnicos, devido à baixa volatilidade e elevada solubilidade do CO2. Contudo, o seu elevado custo limita sua aplicaÃÃo em processos de separaÃÃo industriais por absorÃÃo. Neste contexto, a impregnaÃÃo de pequenas quantidades de LIs em suportes porosos tÃm sido recentemente reportada para prÃpositos de captura de CO2. Estruturas metalorgÃnicas tÃm sido apontadas como um adsorvente adequado devido a sua elevada capacidade de adsorÃÃo de CO2 e à possibilidade de acomodar molÃculas que lhes confiram novas funcionalidades. Neste trabalho, investigamos a adsorÃÃo de CO2 na estrutura metalorgÃnica Cu-BTC impregnada com lÃquidos iÃnicos por tÃcnicas experimentais e de simulaÃÃo molecular. Os lÃquidos iÃnicos utilizados para impregnaÃÃo foram o hexafluorofosfato de 1-butil-3- metilimidazÃlio (BMIM-PF6) e o bis(trifluorometilsulfonil)-imida de 1-butil-3-metilimidazÃlio (BMIM-Tf2N). No Ãmbito experimental, amostras comerciais de Cu-BTC foram impregnadas com LIs em diversas concentraÃÃes em peso (1, 5 e 10 wt%). Os materiais impregnados foram caracterizados por diversas tÃcnicas de caracterizaÃÃo e avaliados em relaÃÃo a adsorÃÃo de CO2. Os resultados mostraram que a impregnaÃÃo de LIs em Cu-BTC reduz a capacidade de adsorÃÃo de CO2, contrariamente ao que foi predito por simulaÃÃo molecular em trabalhos prÃvios. No contexto da simulaÃÃo molecular, foram realizadas simulaÃÃes de impregnaÃÃo para gerar estruturas impregnadas com diferentes quantidades de LI. SimulaÃÃes de adsorÃÃo de CO2, CH4 e N2 nas estruturas geradas foram realizadas utilizando o ensemble Grande CanÃnico (μVT) para avaliar a presenÃa de LI na estrutura da Cu-BTC. Observou-se que a presenÃa de LI em vÃrias concentraÃÃes aumentou a capacidade adsortiva de CO2 a baixas pressÃes (atà ~ 3 bar), enquanto a adsorÃÃo dos outros gases nÃo foi significativamente alterada. Contudo, a baixas concentraÃÃes impregnada (5 %wt), a adsorÃÃo de CO2 nÃo foi sensÃvel à presenÃa do LI. Por outro lado, quando foi aumentada a quantidade de LI impregnada em nossos experimentos, houve uma rÃpida degradaÃÃo das propriedades texturais do material, conforme observado para amostra impregnada com 10 wt% de BMIM-PF6. Assim, aparentemente, os poros da Cu-BTC sÃo pequenos para incorporar lÃquidos iÃnicos nas concentraÃÃes que teoricamente levariam a maiores quantidades adsorvidas de CO2. / A separaÃÃo de CO2 a partir de misturas gasosas industriais consiste em um importante tema tanto do ponto de vista cientÃfico quanto ambiental. O interesse suscitado pelo tema està diretamente relacionado à problemÃtica da presenÃa do diÃxido de carbono tanto nos gases de combustÃo (flue gas) quanto no gÃs natural (GN) e biogÃs. A absorÃÃo usando aminas à uma tecnologia madura que tem sido utilizado na indÃstria do gÃs natural para remoÃÃo de CO2. No entanto, apresenta algumas desvantagens, tais como corrosÃo dos equipamentos e alto consumo de energia para regenerar o absorvente. LÃquidos iÃnicos (LIs) tÃm sido propostos como uma alternativa aos solventes orgÃnicos, devido à baixa volatilidade e elevada solubilidade do CO2. Contudo, o seu elevado custo limita sua aplicaÃÃo em processos de separaÃÃo industriais por absorÃÃo. Neste contexto, a impregnaÃÃo de pequenas quantidades de LIs em suportes porosos tÃm sido recentemente reportada para prÃpositos de captura de CO2. Estruturas metalorgÃnicas tÃm sido apontadas como um adsorvente adequado devido a sua elevada capacidade de adsorÃÃo de CO2 e à possibilidade de acomodar molÃculas que lhes confiram novas funcionalidades. Neste trabalho, investigamos a adsorÃÃo de CO2 na estrutura metalorgÃnica Cu-BTC impregnada com lÃquidos iÃnicos por tÃcnicas experimentais e de simulaÃÃo molecular. Os lÃquidos iÃnicos utilizados para impregnaÃÃo foram o hexafluorofosfato de 1-butil-3- metilimidazÃlio (BMIM-PF6) e o bis(trifluorometilsulfonil)-imida de 1-butil-3-metilimidazÃlio (BMIM-Tf2N). No Ãmbito experimental, amostras comerciais de Cu-BTC foram impregnadas com LIs em diversas concentraÃÃes em peso (1, 5 e 10 wt%). Os materiais impregnados foram caracterizados por diversas tÃcnicas de caracterizaÃÃo e avaliados em relaÃÃo a adsorÃÃo de CO2. Os resultados mostraram que a impregnaÃÃo de LIs em Cu-BTC reduz a capacidade de adsorÃÃo de CO2, contrariamente ao que foi predito por simulaÃÃo molecular em trabalhos prÃvios. No contexto da simulaÃÃo molecular, foram realizadas simulaÃÃes de impregnaÃÃo para gerar estruturas impregnadas com diferentes quantidades de LI. SimulaÃÃes de adsorÃÃo de CO2, CH4 e N2 nas estruturas geradas foram realizadas utilizando o ensemble Grande CanÃnico (μVT) para avaliar a presenÃa de LI na estrutura da Cu-BTC. Observou-se que a presenÃa de LI em vÃrias concentraÃÃes aumentou a capacidade adsortiva de CO2 a baixas pressÃes (atà ~ 3 bar), enquanto a adsorÃÃo dos outros gases nÃo foi significativamente alterada. Contudo, a baixas concentraÃÃes impregnada (5 %wt), a adsorÃÃo de CO2 nÃo foi sensÃvel à presenÃa do LI. Por outro lado, quando foi aumentada a quantidade de LI impregnada em nossos experimentos, houve uma rÃpida degradaÃÃo das propriedades texturais do material, conforme observado para amostra impregnada com 10 wt% de BMIM-PF6. Assim, aparentemente, os poros da Cu-BTC sÃo pequenos para incorporar lÃquidos iÃnicos nas concentraÃÃes que teoricamente levariam a maiores quantidades adsorvidas de CO2.

The interaction between two proteins into salt aqueous solutions is investigated throughout this thesis. Experiments, modeling and molecular simulations were carried out to get a better understanding of the phenomenon. Bovine serum albumin was used as a model protein. An analytical expression for the structure factor for globular proteins in aqueous solution is presented in this work. This expression was obtained considering an intermolecular potential given by the sum of a hard core, a van der Waals attractive and a screened Coulomb contribution. Experimental data of Small Angle X-Ray Scattering for bovine serum albumin in aqueous solutions containing sodium salts at different protein concentrations and pH values are also presented. The expression developed for the structure factor describes accurately these experimental data provided a dependence of the attractive parameter on protein concentration is established. An expression for the osmotic pressure was derived from the structure factor. With attractive parameters adjusted from X-ray scattering data, the osmotic pressure of bovine serum albumin aqueous solutions could be predicted with very good agreement with experimental data. A derivation of the thermodynamic potentials, such as the chemical potential, using the new osmotic equation of state is presented. Applying the phase equilibrium criterion, the fluid-fluid phase equilibrium for bovine serum albumin in salt aqueous solution was calculated. Although such separation was not experimentally observed at the isoelectric point, it was indeed experimentally observed for a pH value below the isoelectric point. The predictions seem to be valuable to discuss how ion specificity affects the phase diagram of proteins. To apply molecular dynamic techniques to simulate how proteins interact to each other in salt aqueous solutions, two new coarse-grained force fields are proposed. The first one, meant for sodium sulfate aqueous solution, avoids the unphysical association observed for non-polarizable atomistic force fields; and allows the prediction of thermodynamic and dynamic properties. The second one, meant for bovine serum albumin in aqueous solution, is used as a new strategy to evaluate the scattering form factor of proteins as a low resolution technique for protein structure prediction. / Nesta tese apresenta-se uma investigação sobre a interação entre duas proteínas em soluções aquosas salinas. Experimentos, modelagem e simulações moleculares foram realizadas para conseguir um melhor entendimento do fenômeno. Albumina de soro bovina foi usada como proteína modelo. Uma expressão para o fator de estrutura de proteínas globulares em solução aquosa é apresentada neste trabalho. Esta expressão foi obtida considerando-se um potencial intermolecular dado pela soma de um núcleo duro, uma contribuição atrativa tipo vander Waals e uma contribuição de potencial coulômbico blindado. Dados experimentais de espalhamento de raios-X a baixos ângulos para a albumina de soro bovino em soluções aquosas contendo sais de sódio com diferentes concentrações de proteína e valores de pH também são apresentados. A expressão desenvolvida para o fator de estrutura descreve com precisão estes dados experimentais, desde que uma dependência entre o parâmetro atrativo com a concentração de proteína seja estabelecida. Uma expressão para a pressão osmótica foi derivada do fator de estrutura. Com parâmetros atrativos ajustados aos dados de espalhamento de raios-X, a pressão osmótica da albumina de soro bovino em solução aquosa pôde ser predita com grande correlação com os dados experimentais. Uma derivação dos potenciais termodinâmicos usando a nova equação osmótica de estado é apresentada. Aplicando o critério de equilíbrio de fases, foi possível calcular o equilíbrio fluido-fluido para a albumina de soro bovino em solução aquosa. Embora tal separação não tenha sido observada experimentalmente em um pH igual ao ponto isoelétrico, ela foi de fato observada experimentalmente para um valor de pH menor do que o ponto isoelétrico. As predições parecem ser valiosas para discutir como a especificidade iônica afeta o diagrama de fases de proteínas. De modo a avaliar como proteínas interagem umas com as outras usando técnicas de dinâmica molecular, dois novos campos de força coarse-grained são propostos. O primeiro, para o sulfato de sódio em solução aquosa, evita a associação não-física que é observada para campos de força atomísticos não-polarizáveis. Este modelo é capaz de prever propriedades dinâmicas e termodinâmicas. O segundo, para a albumina de soro bovino em solução aquosa, é usado como uma nova estratégia para avaliar o fator de forma de espalhamento de proteínas como uma ferramenta de baixa resolução na predição de estruturas proteicas.