Zeolites are crystalline aluminosilicates with diverse structures and uniform porosities. They are widely used as catalysts, adsorbents and ion-exchangers in industry. Direct or post modifications optimize the performance of zeolites for different applications. In this thesis, IZM-2 and TON-type zeolites were synthesized, modified and studied. In addition, FAU-type zeolite and silicoaluminophosphate (SAPO) molecular sieves were applied as templates for the preparation of microporous carbons. In the first part of this thesis, the IZM-2 zeolite with an unknown structure was synthesized. We focused on the increasing the secondary porosity and the varied framework compositions upon post modifications. The structure determination of this IZM-2 zeolite was hindered by the small size of crystals. In the second part of this thesis, the synthesis composition was directly modified in order to increase the crystal sizes. IZM-2 crystals were enlarged by excluding the aluminium atoms from the framework. The micropores of the obtained pure-silica polymorphs were activated by ion-exchanging alkali-metal ions with protons. Typically, TON-type zeolites that are synthesized at hydrothermal conditions under stirring have needle-shaped crystals. In the third part of this thesis, snowflake-shaped aggregates were produced by using static hydrothermal conditions for the synthesis of TON-type zeolites. The effects of synthesis parameters on the growth and morphology of crystals were discussed in detail. In the last part of this thesis, microporous carbons with a structural regularity were prepared by chemical vapour deposition (CVD) of propylene using a silicoaluminophosphate (SAPO-37) template. Compared to the conventional zeolite templates, the SAPO template could be removed under mild conditions, without using hydrofluoric acid, and the generated carbons had a large specific surface area and a high fraction of ultrasmall micropores. / <p>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 3: Manuscript. Paper 4: Manuscript.</p>

This thesis combines solid-state nuclear magnetic resonance (NMR) spectroscopy, X-ray diffraction (XRD), chemical synthesis, isotopic enrichment and density-functional theory (DFT) calculations to provide insight into a number of microporous materials. The first class of materials studied is metal-organic frameworks (MOFs), where the presence of paramagnetic ions has a range of effects on the ¹³C NMR spectra, depending on the nature of the ligand-metal interactions. For the Cu²⁺-based MOFs, HKUST-1 and STAM-1, the assignment of the NMR spectra is non-intuitive, and unambiguous assignment requires specific ¹³C labelling of the organic linker species. It is shown that ¹³C NMR spectra of these two MOFs could act as a sensitive probe of the nature of “guest” molecules bound to the Cu²⁺. The second class of materials is aluminophosphates (AlPOs). It is shown that, using a series of relatively simple linear relationships with the crystal structure, the NMR parameters calculated by DFT (with calculation times of several hours) can be predicted, often with experimentally-useful accuracy, in a matter of seconds using the DIStortion analysis COde (DISCO), which is introduced here. The ambient hydration of the AlPO, JDF-2, to AlPO-53(A) is shown to occur slowly, with incomplete hydration after ~3 months. The resulting AlPO-53(A) is disordered and some possible models for this disorder are investigated by DFT. The final class of materials is gallophosphates (GaPOs), particularly GaPO-34 and related materials. The two as-prepared forms of GaPO-34 are characterised by solid-state NMR, and their calcination investigated by TGA and in-situ powder XRD. An unusual dehydrofluorinated intermediate phase is isolated and characterised for the first time by solid-state NMR. The fully calcined material is shown to be stable under anhydrous conditions, but hydrates rapidly in air. The hydrated material is stable under ambient conditions, but collapses upon heating. Partial dehydration without collapse is achieved by gentle heating or room-temperature evacuation. The impurity phases, GaPO₄ berlinite and GaPO-X are investigated by solid-state NMR and, while the structure of GaPO-X remains unknown, much structural information is obtained.

Transwell inserts with microporous membranes, available from multiple commercial sources, have been widely used for various mammalian cell culture applications, including the reduction of cell culture mixing. In this study, we examined the feasibility and functionality of using this technology for separating human embryonic stem cells (hESCs) from their respective feeder cells. We found that when hESCs were propagated on transwell inserts positioned directly above feeder cells grown in a separate dish, the hESCs could be maintained in an undifferentiated state for over 10 passages with no change in their basic pluripotent characteristics. In parallel with our transwell insert experiments, we also evaluated the ability of a new defined, xeno-free medium, HEScGRO™, to enhance the animal-free characteristics of the transwell insert-based culture system. Results from our studies demonstrate that HEScGRO™ medium assists in maintaining the pluripotent characteristics of hESCs propagated in the transwell insert- based culture system. These combined results represent a significant development in properly segregating stem cells from their feeders, thus eliminating cell mixing, contamination, and providing the cells with a superior environment for nourishment and controlled self-renewal. Overall, this development in hESC propagation could have wide-reaching applications for self-renewal and differentiation studies within the field of stem cell biology.

Les matériaux nanoporeux (méso- et/ou micro-poreux) visent des applications en relation avec les phénomènes d’adsorption tels que la catalyse, la dépollution, le stockage de gaz ou d’énergie,… Récemment, différents types de synthèses ont donc été développés pour contrôler la porosité et l’adapter aux applications visées : synthèse par voie directe, procédé de nanomoulage, technique de réplication réactive. Pour la très grande majorité d’entre elles, elles servent à l’élaboration des matériaux oxydes méso- et micro-poreuses. L’objectif de ce travail de thèse a donc été d’étendre ces procédés à une gamme de matériaux plus large au niveau des compositions chimiques, tout en gardant un contrôle de la porosité. En effet, les oxydes poreux ont un champ d’application limité du fait, par exemple, de leur température maximale d’utilisation, de leur fragilité sous certaines atmosphères ou encore, dans certains cas, de leurs propriétés d’adsorption mal adaptées. Afin de réduire ces limitations, nous avons cherché à étendre la gamme de composition chimique des matériaux poreux dans le domaine non-oxyde (carbone, céramiques de type nitrure, …) tout en contrôlant leur porosité. Pour cela, différentes approches ont été utilisées. La première approche a consisté à étudier mécanisme de formation des matériaux carbonés mésostructurés obtenus directement par l’auto-assemblage d’un tensioactif et d’un polymère précurseur de carbone. Nous avons alors pu déterminer les paramètres pertinents à contrôler pour la reproductibilité des synthèses ayant lieu, aussi bien, en phase aqueuse que par évaporation de solvant. Des analogies avec les mécanismes de formation des matériaux siliciques ont pu être mises en évidence. [...] / Nanoporous materials (meso-and / or micro-porous) target applications in relation to the adsorption phenomena such as catalysis, waste removal, gas or energy storage.... Recently, various types of syntheses have been developed to control the porosity and adapted to applications: direct route synthesis, nanocasting process, reactive templating. For most of them, they are used for the preparation of meso-and micro-porous oxide materials. The objective of this thesis was therefore to extend these methods to a wider range of materials in chemical composition, while keeping control of the porosity. Indeed, the porous oxides have a limited scope because, for example, their maximum operating temperature, their fragility under certain atmospheres or in some cases, their adsorption properties, are unsuitable. To reduce these limitations, we searched to extend the range of chemical composition of porous materials in the non-oxide field (carbon, nitride ceramics,...) while controlling their porosity. For this, different approaches were used. The first approach consisted to study formation mechanism of mesostructured carbon materials obtained directly by the self-assembly of a surfactant and a polymer carbon precursor. We were then able to determine the relevant parameters to control syntheses reproducibility taking place both in aqueous phase and by solvent evaporation. Analogies with the formation mechanisms of siliceous materials have been identified. With a better understanding of the formation mechanisms, we declined in a second time this method of direct synthesis to other materials by varying the nature of the precursors. Thus, a "green" synthesis of a carbonaceous material with ordered mesoporosity was developed in the absence of all toxic reagents such as formaldehyde and phenol, by using a natural precursor, the mimosa tannin. [...]

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / Population growth, industrial and agricultural activities produce daily considerable amounts of wastewaters containing numerous organic pollutants (organic dyes, benzene, toluene, ethylbenzene and xylene), which are thrown directly into the environment, causing health effects to humans as well as aquatic beings. Dyes are widely used in several industrial segments including cosmetics, leather, printing, paper, food and textile, being considered hazardous pollutants due to high chemical stability in aqueous medium, possessing also no biodegradable nature making their removal difficult. Among the number of methods employed for the treatment of aqueous effluents, adsorption has been considered one of the most promising ones owing to the high efficacy, convenience and feasibility. Activated carbon is certainly the most used adsorbent owing to physical properties (high surface area and porosity) as well as surface chemistry. However, activated carbons are usually inefficient to remove high molecular weight molecules such as dyes, owing to the microporous structure. Thus, a novel type of micro-mesoporous carbon has been synthesized in the work employing a mechanosynthesized silica template (HZSM-5/SBA-15) in variable mass proportions, as well as palm oil cooking waste as carbon source. Materials were characterized by X-ray diffraction (XRD), N2 adsorption-desorption isotherms using BET model, Fourier-transform infrared spectroscopy, scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM) and zeta potential determination. Scanning electron microscopy images showed the efficiency of the mechanosynthesis to all mass proportions used, while the textural properties were strongly influenced by the presence of SBA-15. X-ray diffraction patterns for ordered mesoporous carbons (OMC’s) confirmed the mantainance of the crystalline order typical of the templates. The resulting mesoporous carbon has been evaluated as adsorbent to different dye molecules, including molecules with distinct sizes and electrical charges. Results revealed that the carbon adsorbent exhibited high affinity for cationic dyes owing to the presence of negatively charged functional groups onto the surface and also that the mesoporous structure favors high diffusion rates leading to a higher adsorption efficiency compared to the other adsorbents studied (activated carbon, SBA-15, SBA-15/HZSM-5-50, OMC-NC). / O crescimento populacional, as atividades industriais e agrícolas produzem diariamente quantidades consideráveis de águas residuais que contém inúmeros poluentes orgânicos (corantes orgânicos, benzeno, tolueno, etilbenzeno e xilenos) que são lançados diretamente no meio ambiente, causando efeitos à saúde dos seres humanos e aquáticos. Os corantes são amplamente utilizados em diversos segmentos industriais, como cosméticos, couro, impressão, papel, alimentos e têxtil e são considerados poluentes perigosos, pois apresentam estabilidade química em meio aquoso e possuem natureza não biodegradável o que dificulta sua remoção. Dentre os diversos métodos de tratamento empregados, a adsorção tem sido considerada uma das tecnologias mais promissoras devido à sua alta eficiência, conveniência e viabilidade. O carvão ativado é certamente o adsorvente mais utilizado devido às suas propriedades físicas (elevada área superficial e porosidade) e químicas de superfície, entretanto, devido a sua estrutura microporosa é ineficiente na remoção de moléculas de elevado peso molecular, tais como os corantes. Dessa forma, neste trabalho foi sintetizado um novo tipo de carbono micro-mesoporoso (OMC) via Nanocasting, a partir de um molde de sílica (HZSM-5/SBA-15), em diferentes proporções mássicas, preparado por cominuição e do resíduo da fritura do óleo de dendê como fonte de carbono. Os materiais foram caracterizados através das análises de difração de raios X (DRX), adsorção-dessorção de nitrogênio a 77 K, espectroscopia na região do infravermelho com transformada de Fourier (FT-IR), microscopia eletrônica de varredura (MEV), microscopia eletrônica de transmissão de alta resolução (MET-AR) e potencial zeta. As imagens de microscopia eletrônica de varredura (MEV) mostraram a eficiência da cominuição para todas as proporções mássicas, enquanto que as propriedades texturais foram fortemente influenciadas pela presença de SBA-15. Os difratogramas de raios X dos carbonos mesoporosos ordenados (OMC’s) confirmaram a manutenção da ordenação cristalina característica dos moldes. O material de carbono resultante foi estudado como adsorvente para diferentes moléculas de corantes, incluindo moléculas com cargas e tamanhos diferentes. Os resultados mostraram que o carbono apresentou alta afinidade para os corantes catiônicos devido a presença de grupos funcionais com cargas negativas em sua superfície, que a estrutura mesoporosa favorece as altas taxas de difusão e uma maior eficiência de adsorção comparado aos demais adsorventes (carvão ativado, SBA-15, SBA-15/HZSM-5-50, OMC-NC). / São Cristóvão, SE

Porous materials (e.g. zeolites, activated carbon, etc.) have found various applications in industry, such as the use as sorbents, catalyst supports and membranes for separation processes. Recently, much attention has been focused on synthesizing porous polymer materials. A vast amount of tailor-made polymeric systems with tunable properties has been investigated. Very often, however, the starting substances for these polymers are of petrochemical origin, and the processes are all in all not sustainable. Moreover, the new polymers have challenged existing characterizing methodologies. These have to be further developed to address the upcoming demands of the novel materials. Some standard techniques for the analysis of porous substances like nitrogen sorption at 77 K do not seem to be sufficient to answer all arising questions about the microstructure of such materials. In this thesis, microporous polymers from an abundant natural resource, betulin, will be presented. Betulin is a large-scale byproduct of the wood industry, and its content in birch bark can reach 30 wt.%. Based on its rigid structure, polymer networks with intrinsic microporosity could be synthesized and characterized. Apart from standard nitrogen and carbon dioxide sorption at 77 K and 273 K, respectively, gas sorption has been examined not only with various gases (hydrogen and argon) but also at various temperatures. Additional techniques such as X-ray scattering and xenon NMR have been utilized to enable insight into the microporous structure of the material. Starting from insoluble polymer networks with promising gas selectivities, soluble polyesters have been synthesized and processed to a cast film. Such materials are feasible for membrane applications in gas separation. Betulin as a starting compound for polyester synthesis has aided to prepare, and for the first time to thoroughly analyse a microporous polyester with respect to its pores and microstructure. It was established that nitrogen adsorption at 87 K can be a better method to solve the microstructure of the material. In addition to that, other betulin-based polymers such as polyurethanes and polyethylene glycol bioconjugates are presented. Altogether, it has been shown that as an abundant natural resource betulin is a suitable and cheap starting compound for some polymers with various potential applications. / Das Bestreben, ölbasierte Produkte durch nachwachsende Rohstoffe zu ersetzen, hat dazu geführt, dass in immer größerer Zahl günstige, reichlich vorhandene Naturstoffe als Ausgangsstoffe für chemische Synthesen untersucht werden. In dieser Arbeit werden Polymere auf Basis von Betulin, einem aus Birkenrinde extrahierten Naturstoff, vorgestellt. Betulin ist zu 30 Gewichtsprozent in Birkenrinde enthalten. Da Betulin ein Nebenprodukt der Holzindustrie ist, ist es kostengünstig und sein Einsatz als Ausgangsstoff äußerst lukrativ. Die ersten Berichte über Betulin-basierte Polymere sind in den 1980er Jahren in Russland und Finnland erschienen, in den Ländern mit großen natürlichen Vorkommen an Birken. Betulin wurde in dieser Arbeit verwendet, um sogenannte mikroporöse Polymere herzustellen. Dies sind Stoffe mit Poren von molekularer Dimension. Mikroporöse Materialien sind wegen ihrer potentiellen Anwendung als Katalysatorträger und Gasseparationsmembranen hochinteressant. Die Klasse mikroporöser Polymere wurde durch die Synthese von unlöslichen Betulin-basierten Polyesternetzwerken erweitert. Außerdem gelang es, lösliche Polyester in Form dünner Filme herzustellen. Diese zeigten vielversprechende Ergebnisse in der Trennung von Stickstoff und Kohlendioxid und weisen somit Potential für die Nutzung als Membran auf. Dies könnte z. B. für Kohlendioxid-Reduzierung in Postcombustion-Verfahren interessant sein. Überdies wurde gezeigt, dass Stickstoffadsorption bei 77 K nicht ohne weiteres als Standardmethode für die Analyse von mikroporösen Materialien geeignet ist und dass die mikroporösen Materialien ferner durch Stickstoffadsorption bei 87 K und andere Gassorptionsmethoden bei verschiedenen Temperaturen zu charakterisieren sind. Diese Arbeit trägt zum besseren Verständnis mikroporöser Polymere bei.

A novel method based on pulse current electrodeposition (PCE) employing four different waveforms was developed and utilized for fabricating membrane-electrode assemblies (MEAs) with low platinum loading for use in low-temperature proton exchange membrane fuel cells. It was found that both peak deposition current density and duty cycle control the nucleation rate and the growth of platinum crystallites. Based on the combination of parameters used in this study, the optimum conditions for PCE were found to be a peak deposition current density of 400 mA cm-2, a duty cycle of 4%, and a pulse generated and delivered in the microsecond range utilizing a ramp-down waveform. MEAs prepared by PCE using the ramp-down waveform show performance comparable with commercial MEAs that employ ten times the loading of platinum catalyst. The thickness of the pulse electrodeposited catalyst layer is about 5-7 µm, which is ten times thinner than that of commercial state-of-the-art electrodes. MEAs prepared by PCE outperformed commercial MEAs when subjected to a series of steady-state and transient lifetime tests. In steady-state lifetime tests, the average cell voltage over a 3000-h period at a constant current density of 619 mA cm-2 for the in-house and the state-of-the-art MEAs were 564 mV and 505 mV, respectively. In addition, the influence of substrate and carbon powder type, hydrophobic polymer content in the gas diffusion layer, microporous layer loading, and the through-plane gas permeability of different gas diffusion layers on fuel cell performance were investigated and optimized. Finally, two mathematical models based on the microhardness model developed by Molina et al. [J. Molina, B. A. Hoyos, Electrochim. Acta, 54 (2009) 1784-1790] and Milchev [A. Milchev, “Electrocrystallization: Fundamentals of Nucleation And Growth” 2002, Kluwer Academic Publishers, 189-215] were refined and further developed, one based on pure diffusion control and another based on joint diffusion, ohmic and charge transfer control developed by Milchev [A. Milchev, J. Electroanal. Chem., 312 (1991) 267-275 & A. Milchev, Electrochim. Acta, 37 (12) (1992) 2229-2232]. Experimental results validated the above models and a strong correlation between the microhardness and the particle size of the deposited layer was established.

A novel method based on pulse current electrodeposition (PCE) employing four different waveforms was developed and utilized for fabricating membrane-electrode assemblies (MEAs) with low platinum loading for use in low-temperature proton exchange membrane fuel cells. It was found that both peak deposition current density and duty cycle control the nucleation rate and the growth of platinum crystallites. Based on the combination of parameters used in this study, the optimum conditions for PCE were found to be a peak deposition current density of 400 mA cm-2, a duty cycle of 4%, and a pulse generated and delivered in the microsecond range utilizing a ramp-down waveform. MEAs prepared by PCE using the ramp-down waveform show performance comparable with commercial MEAs that employ ten times the loading of platinum catalyst. The thickness of the pulse electrodeposited catalyst layer is about 5-7 µm, which is ten times thinner than that of commercial state-of-the-art electrodes. MEAs prepared by PCE outperformed commercial MEAs when subjected to a series of steady-state and transient lifetime tests. In steady-state lifetime tests, the average cell voltage over a 3000-h period at a constant current density of 619 mA cm-2 for the in-house and the state-of-the-art MEAs were 564 mV and 505 mV, respectively. In addition, the influence of substrate and carbon powder type, hydrophobic polymer content in the gas diffusion layer, microporous layer loading, and the through-plane gas permeability of different gas diffusion layers on fuel cell performance were investigated and optimized. Finally, two mathematical models based on the microhardness model developed by Molina et al. [J. Molina, B. A. Hoyos, Electrochim. Acta, 54 (2009) 1784-1790] and Milchev [A. Milchev, “Electrocrystallization: Fundamentals of Nucleation And Growth” 2002, Kluwer Academic Publishers, 189-215] were refined and further developed, one based on pure diffusion control and another based on joint diffusion, ohmic and charge transfer control developed by Milchev [A. Milchev, J. Electroanal. Chem., 312 (1991) 267-275 & A. Milchev, Electrochim. Acta, 37 (12) (1992) 2229-2232]. Experimental results validated the above models and a strong correlation between the microhardness and the particle size of the deposited layer was established.

Accuracy in the effective diffusion coefficient of the gas diffusion layer (GDL)/microporous layer (MPL) is important to accurately predict the mass transport limitations for high current density operation of polymer electrolyte membrane (PEM) fuel cells. All the previous studies regarding mass transport limitations were limited to pure GDLs, and experimental analysis of the impact of the MPL on the overall diffusion in the porous GDL is still lacking. The MPL is known to provide beneficial water management properties at high current operating conditions of PEM fuel cells but its small pore sizes become a resistance in the diffusion path for mass transport to the catalyst layer. A modified Loschmidt cell with an oxygen-nitrogen mixture is used in this work to determine the effect of MPL on the effective diffusion coefficients. It is found that Knudsen effects play a dominant role in the diffusion through the MPL where pore diameters are less than 1 μm. Experimental results show that the effective diffusion coefficient of the MPL is only about 21% that of its GDL substrate and Knudsen diffusion accounts for 80% of the effective diffusion coefficient of the GDL with MPL measured in this study. No existing correlations can correlate the effective diffusion coefficient with significant Knudsen contribution.

En funktionsbeläggning består av ett polymert material som beläggs till en textil yta. Denna typ av beläggning används för funktionsplagg och det belagda materialet har som uppgift att skydda användaren från vatten samtidigt som den har god ånggenomsläpplighet. För att tvärbinda funktionsbeläggningen och öka dess hållfasthet appliceras ett översta skikt av polymer som kallas topcoat. En topcoat innehåller tvärbindande ämnen som till exempel isocyanater eller formaldehyd. Dessa ämnen är mycket miljö- och hälsoskadliga. Denna studie har genomförts i syfte att undersöka möjligheten till en reducering av mängden topcoat och därmed minskning av skadliga kemikalier, i en funktionsbeläggning. En mikroporös polyuretanbeläggning applicerades på en polyesterväv med valsrakling. Därefter belades två vattenbaserade topcoats innehållande olika tvärbindare: en med formaldehyd och en med isocyanater, genom luftrakling. Genom att späda den ena topcoaten med olika mängd vatten, variera lutningen av beläggningskniven och ändra knivens tryck mot väven vid beläggning utvecklades sex olika material. Väven med beläggning och olika variation av topcoat testades sedan med avseende på kvalitet. Tester av materialens vattentäthet, ånggenomsläpplighet och nöthållfasthet utfördes. Mängden applicerad topcoat undersöktes genom areaviktoch tjockleksmätning. De belagda ytorna granskades i mikroskop för att analysera eventuella variationer mellan materialen. De belagda materialen var inte vattentäta (&lt;100 cm vattenpelare). Studien visar dock att materialet belagt med en formaldehydbaserad topcoat som spätts med 68 % vatten visar statistiskt säkerställt högre medelvärde i vattentäthetstestet, jämfört med det material som belagts på samma vis men med den ospädda varianten av samma topcoat. Resultaten från areavikts- samt tjockleksmätningen visade inte med säkerhet om vinkeln på knivens lutning eller dess tryck mot väven hade någon påverkan på mängden topcoat som belades. Alla material med de spädda varianterna av topcoat visade god ånggenomsläpplighet, vilken också förbättrades avsevärt efter tvätt samtidigt som materialens vattentäthet inte försämrades i samma skala. Detta resultat är mycket intressant då bibehållen vattentäthet i kombination med god ånggenomsläpplighet efter tvätt är en viktig egenskap för funktionsbeläggningar. Slutledningsvis visar resultaten på möjligheter i att späda topcoaten innan applicering och därigenom uppnå intressanta materialegenskaper i kombination med minskad kemikalieanvändning. Vidare undersökningar krävs dock för att säkerställa eftersträvad vattentät funktion.