Yes / The synthesis of metal–organic frameworks with large three-dimensional channels that are permanently porous and chemically stable offers new opportunities in areas such as catalysis and separation. Two linkers (L1=4,4′,4′′,4′′′-([1,1′-biphenyl]-3,3′,5,5′-tetrayltetrakis(ethyne-2,1-diyl)) tetrabenzoic acid, L2=4,4′,4′′,4′′′-(pyrene-1,3,6,8-tetrayltetrakis(ethyne-2,1-diyl))tetrabenzoic acid) were used that have equivalent connectivity and dimensions but quite distinct torsional flexibility. With these, a solid solution material, [Zr6O4(OH)4(L1)2.6(L2)0.4]⋅(solvent)x, was formed that has three-dimensional crystalline permanent porosity with a surface area of over 4000 m2 g−1 that persists after immersion in water. These properties are not accessible for the isostructural phases made from the separate single linkers. / Financial support from EPSRC under EP/H000925, access to the HPC service ARCHER via EP/L000202. S.N. thanks the EU for a Marie Curie fellowship (PIEF-GA-2010-274952). C.M.-G. thanks the Spanish MINECO for a Ramón y Cajal Fellowship (RYC-2012-10894).

The experimental data and results demonstrated here illustrate the preparation and application of mesoporous metal oxides in energy storage, adsorption, and catalysis. First, a new method of controlling the pore size and wall thickness of mesoporous silica was developed by controlling the calcination temperature. A series of such silica were used as hard templates to prepare the mesoporous metal oxide Co₃O₄. Using other methods, such as varying the silica template hydrothermal treatment temperature, using colloid silica, varying the materials ratio etc., a series of mesoporous β-MnO₂ with different pore size and wall thickness were prepared. By using these materials it has been possible to explore the influence of pore size and wall thickness on the rate of lithium intercalation into mesoporous electrode. There is intense interest in lithium intercalation into titanates due to their potential advantages (safety, rate) replacing graphite for new generation Li-ion battery. After the preparation of an ordered 3D mesoporous anatase the lithium intercalation as anode material has been investigated. To the best of our knowledge, there are no reports of ordered crystalline mesoporous metal oxides with microporous walls. Here, for the first time, the preparation and characterization of three dimensional ordered crystalline mesoporous α-MnO₂ with microporous wall was described, in which K+ and KIT-6 mesoporous silica act to template the micropores and mesopores, respectively. It was used as a cathode material for Li-ion battery. Its adsorption behavior and magnetic property was also surveyed. Following this we described the preparation and characterization of mesoporous CuO and reduced Cu[subscript(x)]O, and demonstrated their application in NO adsorption and delivery. Finally a series of crystalline mesoporous metal oxides were prepared and evaluated as catalysts for the CO oxidation.

Hydrogen is considered as an alternative clean energy source due to the depletion of fossil fuels and related environmental problems. Steam reforming of bio-ethanol, has excellent potential for hydrogen production, with CO2 neutrality. Ni, Pd and Pt are the most active metals for steam reforming of ethanol. Improving catalytic activity of supported Ni catalyst by incorporating small amount of Pd or Pt is a successful method for increasing activity and stability of the catalyst. Development of active and stable catalysts with low coke formation and high hydrogen yield attracted major attention of researchers in recent decades. MCM-41 supported bimetallic mesoporous catalytic materials containing well dispersed Ni and Pd nanoballs were synthesized following an impregnation procedure. TEM images and XRD analysis of these materials indicated the formation of nickel and palladium nanoballs of 15-25 nm and 5-8 nm respectively, within the synthesized materials. These materials have quite narrow pore-size distributions in the range of 1-5 nm. In the calcined materials, nickel was in Ni+3 and Ni+2 states, however in the reduced sample most of the nickel was in Nio state, together with some NiO. Formation of NiOx crystals takes place after the calcination step. Impregnation of palladium into Ni/MCM-41 caused a decrease in the reduction temperature of NiO for about 50oC. Activity of the catalytic materials were tested in the reaction of steam reforming of ethanol.all the catalysts showed high conversion and quite high hydrogen yield over 400 oC. PdNi impregnated MCM-41 supported catalysts showed higher conversion of ethanol but lower hydrogen yield than Ni impregnated catalysts due to methane formation in the case of Pd incorporation. However, MCM-41 does not show enough hydrothermal stability for steam reforming of ethanol reaction. SBA-15 has very similar physical properties of MCM-41 with larger pores and high hydrothermal stability. Ceria also has widespread applications in catalysis area with its excellent oxygen buffering capacity. It can be used as catalyst support and also an improving agent for silica supports. Mesoporous silica SBA-15 with ordered pore structure was synthesized following a hydrothermal procedure and then bimetallic Ni-Ce and Pd-Ni-Ce incorporated mesoporous silica catalysts were prepared and tested in steam reforming of ethanol. On the other hand, ceria enriched silica structures i.e cerium/silicate composites were also synthesized. However the syntheses were unsuccessful due to the thermal sintering of ceria. Addition of ceria to the support structure decreased coke formation significantly.. According to the thermal gravimetric analysis studies conducted after ethanol steam reformin reaction at 600 oC, coke formation with Ni-SBA-15 (Ni/Si=0.10) catalyst was 40% and it was 10% with NiCe-SBA-15 (Ni/Si=0.10, Ce/Si=0.50) Activity test results obtained with Ni incorporated silica catalysts in steam reforming of ethanol gave high hydrogen yield over 4 (max. 6) and complete conversion of ethanol at 600 oC. SBA-15 found to be more stable catalyst than MCM-41 in the steam reforming of ethanol reaction. The highest hydrogen yield values were achieved by AlMCM-41 supported Ni-Ce impregnated catalysts. Aluminum in the slica matrix (3% wt.) increased the catalytic activity significantly, by giving acidic properties to the catalyst. Simultaneous and consecutive Ni and Ce impregnation were also examined. AlMCM-41 supported, consecutively Ce and Ni impregnated catalysts with Ce/Si and Ni.Si molar ratio sof 0.10, showed very high catalytic activity (5.8 at the beginning). AlMCM-41 supported catalyst were less stable because of high activity and consequently coke formation.

Nous visons dans ce travail de thèse à développer une méthodologie de fonctionnalisation par chimie click des silices hybrides synthétisées par voie sol-gel. La réaction click de cycloaddition azoture-alcyne catalysée au cuivre (CuAAC) offre une tolérance exceptionnelle pour les fonctions organiques en plus de conversions très élevées. Dans cette optique, nous avons mis en œuvre en premier lieu des matériaux clickables à base d'organosilice pure (organosilice à mésoporosité périodique (PMO) et silsesquioxanes pontés (BS)) qui ont permis une conversion quasi-quantitative de greffage par CuAAC. Nous avons ensuite utilisé cette particularité pour contrôler les propriétés de surface des BS en modifiant leur caractère hydrophile/lipophile. Dans le second axe de travail, nous nous sommes intéressés à l'apport de la chimie click pour la préparation de nanoparticules mésoporeuses de silice multifonctionnelles, dites mécanisées, pour des systèmes à délivrance contrôlée de principes actifs. / The present work aims to develop a trustful methodology of functionalization for hybrid silica materials made by the sol-gel process using the copper-catalyzed alkyne-azide cycloaddition (CuAAC)Click reaction. This transformation can be highly useful in materials science thanks to its high conversions and the excellent functional group tolerance. In this prospect, we have synthesized fully clickable bridged silisesquioxanes and periodic mesoporous organosilica that show high extents of click grafting. CuAAC was then used for tailoring the surface of bridged silsesquioxane and fine-tuning the hydrophilic/lipophilic balance. Finally, the click reaction was used as an efficient way to obtain multiply functionalized mesoporous silica nanoparticles in order to make nanomachines for controlled delivery of cargo molecules.

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Thesis (MSc)--University of Stellenbosch, 2011. / ENGLISH ABSTRACT: In this thesis the synthesis of a wide range of model and siloxane functionalized N-(n-propyl)-1-(2-pyridyl and quinolyl)-imine ligands (L1-L6) are described. Functionalized ligands (L4-L6) were obtained by the reaction of the pyridyl and quinolyl aldehydes with 3-aminopropyltriethoxysilane. Model ligands were characterized by FT-IR and 1H NMR spectroscopy while 13C{1H} NMR spectroscopy was additionally used for functional ligand characterization. Functionalized complexes of both Pd(II) and Cu(I) were found to be more thermally stable than their model counterparts. Overall the model Pd(II) complexes showed a higher thermal stability than the model Cu(I) complexes. Ligands (L1-L6) were reacted with either Pd(II) or Cu(I) metal precursors to produce both the model and functionalized Pd(II) (C1-C6) and Cu(I) (C7-C12) metal complexes. These metal complexes were all characterized by FT-IR spectroscopy, 1H NMR and UV/Vis spectroscopy for the model Cu(I) complexes. Functionalized complexes were additionally characterized with 13C{1H} NMR spectroscopy. Siloxane functionalized complexes of Pd(II) and Cu(I) were immobilized on MCM-41 and SBA-15 silica materials to produce heterogenized immobilized catalysts. These immobilized catalysts were characterized by a wide range of solid state techniques including: BET nitrogen adsorption/desorption, scanning electron microscopy (SEM), thermal gravimetric analysis (TGA), ICP-AES, FT-IR spectroscopy, powder XRD and solid state 13C{1H} NMR spectroscopy. ICP-AES and BET surface analysis showed that better complex immobilization occurred for SBA-15 supported materials despite SBA-15 having a significantly lower surface area than MCM-41. This higher immobilization was ascribed to the larger pore sizes of SBA-15 (50 Å) vs. that of MCM-41 (26 Å). Immobilized catalysts were tested for the oxidation of benzyl alcohol to benzaldehyde. Immobilization had a positive effect on the catalytic activity of the Pd(II) complexes with higher conversions being observed for immobilized Pd(II) catalysts when compared to their model analogues. Overall the MCM-41 immobilized Pd(II) catalysts showed a higher increase in activity than SBA-15 immobilized catalysts. For Ti-doped supports a generally higher activity was seen for the Ti-SBA-15 system. The Cu(I) systems however were not as effective in the oxidation reactions. / AFRIKAANSE OPSOMMING: In hierdie tesis word die sintese van `n wye reeks model sowel as gefunksioneerde N-(n-propiel)-1-(2-piridiel en kinoliel)-imien ligande (L1-L6) beskryf. Gefunksioneerde ligande (L4-L6) is gevorm deur die reaksie van piridiel en kinoliel aldehied met 3-amniopropieltriëtoksiesilaan. Model ligande is gekaraktariseer deur FT-IR en 1H KMR spektroskopie terwyl 13C{1H} KMR spektroskopie addisioneel gebruik is vir die karaktarisering van die gefunksioneerde ligande. Ligande (L1-L6) is gereageer met Pd(II) of Cu(I) metaal voorgangers om beide model sowel as gefunksioneerde Pd(II) (C1-C6) en Cu(I) (C7-C12) metaal komplekse op te lewer. Hierdie metaal komplekse is almal gekaraktariseer deur FT-IR, 1H KMR en UV/Vis spektroskopie vir die model Cu(I) komplekse. Gefunksionalseerde komplekse is addisioneel gekaraktariseer deur gebruik te maak van 13C{1H} KMR spektroskopie. Dit is gevind dat gefunksionaliseerde komplekse van beide Pd(II) sowel as Cu(I) termies meer stabiel was as hulle ooreenstemmende model komplekse. Oor die algemeen het die Pd(II) komplekse hoër termiese stabiliteit as die Cu(I) komplekse getoon. Siloksaan gefunksioneerde komplekse van Pd(II) en Cu(I) is geimmobiliseer op MCM-41 en SBA-15 silika materiale om heterogene geimmobiliseerde katalisatore op te lewer. Hierdie geimmobiliseerde katalisatore is gekaraktariseer deur van `n wye reeks vaste toestand tegnieke gebruik te maak. Hierdie suit in: SEM, TGA, ICP-AES, FT-IR, poeier XRD en vaste toestand 13C{1H} KMR spektroskopie. ICP-AES en BET oppervlak analieses het getoon dat beter kompleks immobilisering vir die SBA-15 silika material plaas gevind het, ondanks die feit dat SBA-15 `n laer oppervlak area beskik. Hierdie hoër graad van immobilisering is toegeskryf aan die groter poriegrootte van SBA-15 (50 Å) teenoor die van MCM-41 (26 Å). Geimmobiliseerde katalisatore is getoets in die oksidasie van bensielalkohol na bensaldehied. Dit is gevind dat die immobilisering van die Pd(II) komplekse op die silika materiaal `n positiewe uitwerking op die aktiwiteit van die katalitiese van die komplekse gehad het. Die hoogste toename in aktiwiteit is gesien vir geimmobiliseerde Pd(II) katalisatore wanneer hulle met hul ooreenstemmende model komplekse vergelyk is. Oor die algemeen is gevind dat MCM-41 geimmobiliseerde Pd(II) katalisatore n hoër toename in aktiwiteit getoon het as die van SBA-15. Vir die Ti-gedokterde silika materiale het die Ti-SBA-15 sisteem oor die algemeen `n hoër aktiviteit getoon as die Ti-MCM-41 sisteem. Die Cu(I) sisteme was egter nie so effektief in oksidasie reaksies nie.

By replacing the intercalation electrode with a porous electrode and allowing lithium to react directly with O₂ from the air, the new rechargeable Li/O₂ battery system was studied. The porous cathode is comprised of carbon, catalyst and binder. The effect of every component was investigated. The catalyst was believed to play an important role in the performance of the electrode. A number of potential materials have been examined as the catalyst for the O₂ electrode. It suggests that the nature of the catalyst is a key factor controlling the performance of the O₂ electrode. Several catalysts based on first row transition metal oxides each with three different morphologies, bulk, nanoparticulate and mesoporous were studied. The influence of the morphology on the discharge and charge voltage, discharge capacity and cyclability were examined. Among all the catalysts studied, α-MnO₂ nanowires was found to be the best candidate. The reversible capacities of 3000 mAhg⁻¹(normalised by the mass of carbon) or 505 mAhg⁻¹ (based on the total mass of cathode + O₂ ) was obtained. Some of other factors, such as type of carbon, type of binder, type of electrolyte, the construction of cathode and the modification of the catalyst were also investigated, even just in the early stage. Capacity fading during cycling is the main problem in all the cases. A number of experiments were carried out to understand and attempt to avoid the fading problem. After successful synthesis of mesoporous α-Fe₂O₃ with unique properties (by Jiao et al.), the application of these materials in conventional Li battery was studied. Mesoporous α-Fe₂O₃ with ordered walls, mesoporous α-Fe₂O₃ with disordered walls and Fe₂O₃ nanoparticles were examined. It was also applied to examine the different factors that influence the rate of conversion electrodes, i.e., Li⁺ and e⁻ transport to and within the particles, as well as the rate of the two-phase reaction, demonstrating that for this conversion reaction electron transport to and within the particles is paramount.