Developing the synthetic control required for the intentional 3-D arrangement of atoms remains a holy grail in crystal engineering and materials chemistry. The explosive development of metal-organic materials in recent decades has shed light on the above problem. Their properties can be tuned by varying the organic and/or inorganic building units. In addition, their crystallinity makes it possible to determine their structures via the X-ray diffraction method. This dissertation will focus on the chemistry and applications of two kinds of metal-organic materials, namely, metal-organic frameworks (MOFs) and metal-organic polyhedra (MOP). MOFs are coordination polymers. Their permanent porosity makes them a good “gas sponge”. In the first section, an isoreticular series of MOFs with dendritic hexacarboxylate ligands has been synthesized and characterized structurally. One of the MOFs in this series, PCN-68, has a Langmuir surface area as high as 6033 m2 g-1. The MOFs also possess excellent gas (H2, CH4, and CO2) adsorption capacity. In the second section, a NbO-type MOF, PCN-46, was constructed based on a polyyne-coupled di-isophthalate linker formed in situ. Its lasting porosity was confirmed by N2 adsorption isotherm, and its H2, CH4 and CO2 adsorption capacity was examined at 77 K and 298 K over a wide pressure range (0-110 bar). Unlike MOFs, MOP are discrete porous coordination nanocages. In the third section, a MOP covered with bulky triisopropylsilyl group was synthesized, which exhibits a thermosensitive gate opening property. This material demonstrates a molecular sieving effect at a certain temperature range, which could be used for gas separation purpose. In the last section, a MOP covered with alkyne group was synthesized through kinetic control. The postsynthetic modification via click reaction with azide-terminated polyethylene glycol turned them into metallomicelles, which showed controlled release of an anticancer drug 5-fluorouracil. In summary, two kinds of metal-organic materials have been discussed in this dissertation, with the applications in gas storage, gas separation, and drug delivery. These findings greatly enrich the chemistry and applications of metal-organic materials.

La détection de faibles quantités de petites molécules volatiles, qu’elles soient polluantes, utilisées comme armes chimiques ou encore explosives présente un intérêt sociétal certain. Les polymères de coordination poreux (PCPs) ou ’Metal-Organic Frameworks‘ (MOFs) sont des solides poreux qui peuvent être décrits par l’association de ligands organiques et de briques inorganiques interagissant par liaisons fortes et définissant une structure cristalline avec des pores de différentes tailles et formes. La large gamme d'application de ces solides (séparation, stockage, biomédecine...) repose sur leurs diversités chimique et structurale. Par exemple, il est possible de synthétiser des MOFs luminescents en utilisant un ligand organique lui-même luminescent. Le coeur tétrazine et ses dérivés sont des bons candidats pour cet objectif, puisqu'ils présentent des propriétés de fluorescence remarquables : émission dans le visible (λem~560 nm), bon rendement quantique. De plus, cette fluorescence peut être modifiée par la présence de molécules riches en électrons, ce qui laisse envisager son utilisation comme capteur moléculaire. Nos travaux se sont de plus focalisés sur des métaux à haut degré d'oxydation (Al(III), Zr(IV)) susceptibles de conférer aux solides une stabilité en milieu aqueux adéquate pour les applications envisagées. Deux acides carboxyliques à base de tétrazine, adaptés à la préparation de MOFs, ont tout d'abord été synthétisés. Le premier a été utilisé pour préparer un MOF à base de zirconium.La structure du solide, et entre autres son caractère flexible, ainsi que ses propriétés optiques ont été étudiées. Particulièrement, ses performances en tant que capteur d'amines aromatiques et de phénol ont été évaluées. La réactivité du second ligand avec les ions lanthanides a aussi été explorée et plusieurs solides ont été isolés, leur structure, caractérisée. Leurs propriétés optiques ont été évaluées, afin d'établir des relations entre la structure du MOF et la fluorescence de la tétrazine. Ensuite, avec ce même ligand, une stratégie de synthèse à ligand mixte a été adoptée pour incorporer la tétrazine dans des MOFs. Il s'agit de partir d'une structure aux propriétés avantageuses (stabilité, porosité) et de substituer une partie de ses ligands organiques ‘inactifs’ par des tétrazines. Ceci peut s'effectuer pendant la synthèse ou via un traitement post-synthétique. Les propriétés optiques des solides obtenus ont été enfin étudiées et leur efficacité en tant que capteur évaluées. / Detection of low concentrations of small organic molecules, which can be hazardous, polluting or used as chemical weapons, represents a societal problem worth addressing. Metal-Organic Frameworks (MOFs) are a class of porous crystalline materials that can be described as an association of inorganic subunits and organic ligands defining an ordered structure with accessible cavities of various size and shape. The wide range of potential applications for these materials (biomedicine, gas separation, catalysis...) relies on their chemical and structural diversity, which allows combining porosity with additional properties. For example, it is possible to synthesize luminescent MOFs through the use of a luminescent organic ligand. The tetrazine core and its derivatives appear as good candidates for such a purpose, as they have a fluorescent emission in the visible spectrum (λem~560 nm) with a good quantum yield. In addition, this fluorescence can be affected by the presence of electron rich molecules, making their use possible as sensors for ions or organic molecules. Our work focused mainly on the design of MOFs based on tetrazine and cations of high charge density (Al(III), Zr(IV)) in order to ensure their stability in water, which is desirable in this field.Two different tetrazine dicarboxylic acids suitable for the preparation of MOFs were first synthesized. The first one was used to prepare a new MOF based on zirconium. The structure of this solid, together with its flexible character and its optical properties were investigated. Especially, its use for the sensing of aromatic amines and phenol was evaluated. The reactivity of the second ligand with lanthanide ions was then investigated and few solids were isolated and structurally characterized. Their optical properties have been studied, in order to establish some relationship between their structure and their fluorescence. Then, with the same ligand, a mixed-ligand strategy has been developed in order to incorporate the tetrazine into MOFs. This involves starting from a non-fluorescent MOF with interesting properties (stability, porosity) and substituting some of the 'inactive' ligands with these tetrazines. This was performed either during the synthesis or as a post-synthetic treatment. The spectroscopic properties of these solids were finally investigated and their efficiencies as sensors evaluated.

No description available.

Globally the combustion of fossil fuels has increased to a greater extent. Carbon dioxide (CO2) a major greenhouse gas isa by-product of such combustion practices. Increase in the quantity of CO2 emissions has resulted in serious environmental issues including global warming, ocean acidification, extreme weather, and much more leaving a direct impact on the human society. To reduce these emissions, we need a more efficient carbon dioxide capturing technology. Using advances in materials science and engineering we can develop newer technologies for the capture of carbon dioxide gas. Metal-organic frameworks (MOFs) constitute a class of three-dimensional porous materials. They have shown applicability in various fields including carbon dioxide capture. A vast variety of MOFs can be synthesized by selecting proper metal salts and organic-linkers to build up the MOF structure. This thesis focuses on the synthesis of MOFs through a sustainable process or green synthesis route. Most of the MOFs in this study have been synthesized at ambient temperature and pressure conditions with deionized water as the primary solvent. A total of eight MOFs were synthesized in this study using two organic-linkers namely, 1,2,4,5-tetrakis(4-carboxyphenyl)-benzene (H4TCPB) and 2,5-dihydroxy-1,4-benzoquinone (H2DHBQ). The metal-salts used were based on hafnium, zirconium, cerium, magnesium, iron and manganese. A number of qualitative and quantitative tests were carried out onthe MOF samples to ensure their quality of produce and performance. The primary focus was to test the materials for their capacity to uptake carbon dioxide (CO2) in a mixture of flue gases. The highest CO2 uptake capacity was recorded to be 3.02 mmol/g (at 293 K and 1 bar) by the H2DHBQ-magnesium based MOF. All the materials showed good results andwere proven to be reusable. All the synthesized MOFs were crystalline in nature, showed a single-phase microstructure and high surface area values. A supplementary study was conducted wherein the powdered MOFs were 3D printed by the Direct Ink Writing (DIW) technique using an alginate binder. The study was satisfactory because the MOFs after being 3D printed, managed to preserve their inherent properties and characteristics. The results were in par with that of their pristine MOF counterparts. / Den globala förbränningen av fossila bränslen har i allt större utsträckning ökat. Koldioxid (CO2) är en avde viktigast växthusgaserna och erhålls som biprodukt från många förbränningsmetoder. Den höga haltenkoldioxid i atmosfären har resulterat i allvarliga miljömässiga konsekvenser inklusive den globaluppvärmningen, försurning av haven, extremt väder och mycket mer som har en direkt påverkan på detmänskliga samhället. För att minska dessa utsläpp behöver vi en mer effektiv koldioxidinfångningsteknologi. Med hjälp av framsteg inom materialvetenskapen kan vi utveckla nyare tekniker för att fångakoldioxid.  Metallorganiska ramverk (MOFs) utgör en klass av tredimensionella porösa material. De har visat siganvändbara inom olika områden inklusive infångning av koldioxid. Många variation av MOF material kansyntetiseras från olika metallsalter och organiska ligander för att bygga upp MOF-strukturen. Dettaexamensarbete fokuserar på syntesen av metallorganiska ramverk via en grön syntesväg och en hållbarprocess. En stor del av MOF materialen som erhölls syntetiserades i rumstemperatur och vid normala tryckmed avjoniserat vatten som det primära lösningsmedlet. Åtta MOFs material syntetiserades i detta projekt med två olika organiska ligander, nämligen, 1,2,4,5-tetrakis(4-karboxifenyl)bensen (H4TCPB) och 2,5-dihydroxy-1,4-bensokinon (H2DHBQ). Metallsalternasom användes i synteserna baserades på hafnium(IV), zirkonium(IV), cerium(IV), magnesium(II), järn(II)och mangan(II). Ett antal kvalitativa och kvantitativa tester genomfördes på MOF:arna för att säkerställaderas kvalitet och prestanda. Det primära fokuset var att testa de olika materialen för deras förmåga att taupp koldioxid (CO2) i en blandning av olika gaser (så som kväve, N2). Den DHBQ-magnesium-baseradeMOF:en uppvisade den högsta CO2-upptagningsförmågan som var 3,02 mmol/g. Alla MOF material visadegoda resultat och visade sig även vara återanvändbara. Alla syntetiserade MOF:ar hade god kristallinitet,uppvisade en singulär fas samt hög ytarea. En kompletterande studie genomfördes där de syntetiserade MOFs materialen (i dess pulverform) 3Dprintades med hjälp av natriumalginat som bindemedel. Studien var lyckad eftersom MOF:arna erhöll entillämplig form/maktrostruktur samtidigt som materialen bevarade sina inneboende egenskaper efter 3Dprintningen.

The process of purifying hydrogen gas using pressure swing adsorption columns heavily relies on highly efficient adsorbents. Such materials must be able to selectively adsorb a large amount of impurities, and must also be regenerated with ease. The work presented in this thesis focuses on a novel class of porous solids, metal-organic frameworks (MOFs), and their potential for use as adsorbents in hydrogen purification processes. MOFs are tuneable structures, a property that can be exploited in order to achieve the desired characteristics that are beneficial for a specific application. The design or selection of MOFs for any separation process however, relies on a thorough understanding of the relationship between a framework’s characteristics and its adsorption and selective properties. In order to identify favourable MOF characteristics for the separation of hydrogen from typical impurities a systematic molecular simulation study is performed on a large group of MOFs. Features such as the presence of short linkers, amine groups and additional aromatic rings, and a high density of linker groups are found to increase the adsorbate - framework interaction strength, and reduce the free volume available inside the pores. Both of these effects are shown to enhance MOF selectivity for impurities. Two promising materials, exhibiting desirable features, Mn MIL-53 and MIL-47, are studied further through a variety of approaches. A combination of experimental work and molecular simulations are employed in order to assess the level of flexibility in Mn MIL-53 on uptake of CO2 and CH4. An investigation of the experimental and simulation adsorption and characterization data indicates that the framework undergoes structural changes, in order to accommodate CO2 molecules, but not CH4. The form of the framework during CO2 uptake is also shown to be strongly influenced by temperature. In the case of MIL-47, adsorption isotherms simulated for a wide range of gases overpredict experimental adsorption data, leading to an in-depth investigation of non-porous effects, force field suitability, and framework rigidity. Ab initio molecular dynamics studies of MIL-47 indicate that the benzene dicarboxylate linkers rotate about their symmetry axis to reach more energetically favourable configurations, an effect responsible for the discrepancies between simulated and experimental isotherms. The effect of MOF flexibility on adsorption is further highlighted in a study of Sc2BDC3, a material able to undergo structural changes in order to accommodate a variety of adsorbates. Molecular simulations show that structural changes in the framework are responsible for the creation of additional CO2 adsorption sites as pressure is increased, whereas methanol adsorption sites occupied at extreme pressure are stabilized by the formation of hydrogen bonds. Finally, the exceptionally robust UiO-66(Zr) and UiO-67(Zr) families of MOFs are analysed using a multi-scale simulation study combining molecular level and process-scale computational work, seeking to compare the materials to commercial adsorbents, and assess whether they are suitable for H2 purification through pressure swing adsorption (PSA). Of the four MOFs studied, UiO-66(Zr)-Br is the most promising, as it significantly outperforms commercial zeolites and activated carbons in H2 purification from steam methane reformer offgas.

Using computational tools ranging from molecular simulations – including both Monte Carlo and molecular dynamics methods – to quantum mechanical (QM) calculations (primarily at density functional theory (DFT) level), this work focuses on addressing some of the challenges faced in molecular simulations of gas adsorption in metal–organic frameworks (MOFs). This work consists of two themes: one concerns gas adsorption in MOFs with coordinatively unsaturated metal sites (cus’s), and the other one deals with predicting and understanding the breathing behaviour of the flexible MOF MIL-53(Sc). It has been shown experimentally that incorporation of cus’s – also known as “open” metal sites or unsaturated metal centres – into MOFs significantly enhances the uptake of certain gases such as CO2 and CH4. As a result of the considerably enhanced, localized guest-molecule interactions with the cus’s, it, however, remains a challenge to predict correctly adsorption isotherms and/or mechanisms in MOFs with cus’s using grand-canonical Monte Carlo (GCMC) simulations based on generic classical force fields. To address this problem, two multi-scale modelling approaches – which combine GCMC simulations with QM calculations – have been proposed in this work. The first approach is based on the direct implementation of a fluid–framework potential energy surface, calculated by a hybrid DFT/ab initio method, in the GCMC simulations. The second approach involves parameterization of ab initio force fields for GCMC simulations of gas adsorption in MOFs with cus’s. This approach focuses on the generation of accurate ab initio reference data, selection of semiempirical model potentials, and force-field fitting through a multi-objective genetic algorithm approach. The multi-scale simulation strategy not only yields adsorption isotherms in very good agreement with experimental data but also correctly captures adsorption mechanisms, including the adsorption on the cus’s, observed experimentally but absent from GCMC simulations based on generic force fields. The second challenge that this work aims to address concerns the “breathing” phenomenon of MOFs, in which the framework structure adapts its pore opening to accommodate guest molecules, for example. The breathing effect gives rise to some exceptional properties of these MOFs and hence promising applications. However, framework flexibility often poses a challenge for computational studies of such MOFs, because suitable flexible force fields for frameworks are lacking and the effort involved in developing a new one is no less a challenge. Here, an alternative to the force-field-based approach is adopted. Ab initio molecular dynamics (AIMD) simulations – which combine classical molecular dynamics simulations with electronic-structure calculations “on the fly” – have been deployed to study structural changes of the breathing MOF MIL-53(Sc) in response to changes in temperature over the range 100–623 K and adsorption of CO2 at 0–0.9 bar at 196 K. AIMD simulations employing dispersion-corrected DFT accurately simulated the experimentally observed closure of MIL-53(Sc) upon solvent removal and the transition of the empty MOF from the closed-pore phase to the very-narrow-pore phase with increasing temperature. AIMD simulations were also used to mimic the CO2 adsorption of MIL-53(Sc) in silico by allowing the MIL-53(Sc) framework to evolve freely in response to CO2 loadings corresponding to the two steps in the experimental adsorption isotherm. The resulting structures enabled the structure determination of the two CO2-containing intermediate and large-pore phases observed by experimental synchrotron X-ray diffraction studies with increasing CO2 pressure; this would not have been possible for the intermediate structure via conventional methods because of diffraction peak broadening. Furthermore, the strong and anisotropic peak broadening observed for the intermediate structure could be explained in terms of fluctuations of the framework predicted by the AIMD simulations. Fundamental insights from the molecular-level interactions further revealed the origin of the breathing of MIL-53(Sc) upon temperature variation and CO2 adsorption. Both the multi-scale simulation strategy for gas adsorption in MOFs with cus’s and the AIMD study of the stimuli-responsive breathing behaviour of MIL-53(Sc) illustrate the power and promise of combining molecular simulations with quantum mechanical calculations for the prediction and understanding of MOFs.

This research explores the synthesis of anthracene and stilbene-based metal-organic framework (MOF) structures as potential scintillating (radioluminescent) materials for use in the detection of gamma radiation. The organic molecules 9,10-anthracenedicarboxylic acid (ADCH2) and trans-4,4’-stilbenedicarboxylic acid (SDCH2), were each used as a linker, in combination with a range of lanthanide metal ions, to synthesize novel three dimensional MOF structures under hydrothermal conditions. With ADCH2, the early period lanthanides yield isostructures with the metal ion in higher coordination (nine) than for those with late period metals (seven). The ADC-MOFs show linker-based photoluminescence properties with well defined vibronic peaks in their emission profile and their emission (λmax~435 nm) blue shifting from that of the ADCH2 powder (~500 nm) and closer to the organic molecule in monomer arrangement (λmax ~ 420 nm). The structures also show photoluminescence lifetimes between 1 and 2 ns, which is similar to the reported value for monomeric anthracene units. The blue-shift and reduction in lifetime, compared to ADCH2, are indicative of minimal π-π interactions amongst the aromatic moieties, thereby limiting the non-radiative relaxation pathways. On exposure to ionizing radiation (protons and g- rays), the ADC-MOFs demonstrated scintillation properties, with a radioluminescence lifetime of ~ 6 ns which is similar to that of the ADCH2 powder. A combination of SDCH2 and lanthanide metal ions produced two isostructured MOFs containing Tm3+ and Er3+, under the hydrothermal synthesis conditions explored. The 3-D structure contained ultra large diamond-shaped pores with dimensions of 16 Å x 30 Å. A blue-shift of fluorescence spectra was observed for the SDC-MOF structures (λmax ~ 425 nm) compared to that of bulk SDCH2 powder (λmax ~475 nm), and closely resembling that of monomeric isolated SDC units (λmax~475 nm). Their photoluminescence lifetime is ~0.76 ns, about half of that observed for SDCH2 powder. The blue shift and reduction in lifetime (compared to SDCH2) is attributed to minimal π-π interactions between SDC units in the MOF structure, thus minimizing associated non-radiative relaxation pathways. The isolation of anthracene and stilbene in MOF structures therefore has the potential to improve their performance as scintillators.

In this work, multinuclear solid-state nuclear magnetic resonance (NMR) spectroscopy is used to investigate a range of inorganic materials, often in combination with DFT (density functional theory) studies. Solid-state NMR is particularly suited to the study of aluminophosphates (AlPOs), as the basic components of their frameworks have NMR active isotopes (²⁷Al, ³¹P, ¹⁷O), as do many of the atoms that comprise the structure directing agent (¹³C, ¹H, ¹⁵N), and the charge-balancing anions (OH⁻, F⁻). A study of the AlPO STA-15 (St Andrews microporous solid-15) provides an introduction to using solid-state NMR spectroscopy to investigate AlPOs. More in-depth studies of AlPO STA-2 (St Andrews microporous solid-2) and MgAPO STA-2 (magnesium-substituted AlPO) examine charge-balancing mechanisms in AlPO-based materials. A range of scandium carboxylate metal-organic frameworks (MOFs), with rigid and flexible frameworks, have been characterised by multinuclear solid-state NMR spectroscopy (⁴⁵Sc, ¹³C and ¹H). The materials studied contain a variety of metal units and organic linkers. ¹³C and ¹H magic-angle spinning (MAS) NMR were used to study the organic linker molecules and ⁴⁵Sc MAS NMR was used to study the scandium environment in the MOFs Sc₂BDC₃ (BDC = 1,4-benzenedicarboxylate), MIL-53(Sc), MIL-88(Sc), MIL-100(Sc) and Sc-ABTC (ABTC = 3,3`,5,5`-azobenzenetetracarboxylate). Functionalised derivatives of Sc₂BDC₃ and MIL-53(Sc) were also studied. The ⁴⁵Sc MAS NMR spectra are found to be strongly dependant on the Sc³⁺ coordination environment. ²⁷Al and ²⁵Mg MAS NMR have been used to study Ti-bearing hibonite samples (of general formula Ca(Al, Ti, Mg)₁₂O₁₉), and results compared to a recent complementary neutron powder diffraction study, in order to investigate the substitution sites for Ti³⁺/⁴⁺ and Mg²⁺. A DFT investigation was also carried out on the aluminium end member, CaAl₁₂O₁₉, due to debate in the literature on the ²⁷Al NMR parameters for the trigonal-bipyramidal site. The substitution of Mg onto the tetrahedral site (M3) and Ti primarily onto one of the octahedral sites (M4) is supported.

The research presented in this thesis aims to assess the capacity of metal organic frameworks with open metal sites for the separation of olefin mixtures. Chapter 1 provides a background to the field, including industrial separation techniques, metal organic frameworks and their applications and the current state-of-the- art for olefin separation. Chapter 3 describes the experimental techniques used in this research. Ethylene and propylene adsorption and desorption isotherms on Ni-CPO-27 and HKUST-1 at a range of temperatures are presented and compared in Chapter 4, and used to calculate isosteric heats of adsorption at varying coverages using the virial method. These pure component isotherms are used in Chapter 5 to predict selectivities for the separation of binary mixtures using ideal adsorbed solution theory. Temperature programmed desorption is used in Chapter 5 to calculate the enthalpy of desorption using Redhead's method and the heating rate variation method, and the two results are compared. The results presented in Chapters 4 and 5 conclude that propylene/ethylene separation is possible using adsorption onto metal organic frameworks with open metal sites. A new in situ environmental gas cell for single crystal X-ray diffraction is developed in Chapter 6, and the challenges encountered during this development process are discussed. The dehydration of one framework, Co-CPO-27, is studied in detail using the environmental gas cell. A dehydrated structure of HKUST-1, obtained using the gas cell, is presented for the first time. Crystal structures for the complete dehydration-adsorption-delivery cycle for biologically active NO on Co-CPO-27 are presented in Chapter 7, showing the utility of the in situ gas cell for prolonged experiments in multiple different gaseous environments. The crystal structure of NO-loaded Co-CPO-27 improves upon the models suggested in the literature, and the treatment of the dual occupancy of the open metal sites by water and NO is discussed in depth. A crystal structure of CO-loaded Co-CPO-27 is obtained for the first time, and crystal structures of Co-CPO-27 in ethylene and propylene environments are presented.

Adsorption processes are widely used for the storage and separation of gases in many industrial and environmental applications. The performance of the process depends strongly on the adsorbent and its interaction with the gases. Therefore, the idea of tailoring the adsorbent to the application by adapting the pore size and/or the chemical composition is very attractive. This work focuses on two groups of customizable hybrid materials: Firstly, in crystalline metal-organic frameworks (MOFs) the chemical and structural properties can be modified by changing the metal-oxide corner or the organic linker. Secondly, periodic mesoporous silica materials can be prepared with different pore sizes and geometries depending on the surfactant and its concentration and additionally modified with organic surface groups. The adsorption behaviour of the materials can be predicted by molecular simulation and thus the influence of modifications can be studied without the need of synthesising the material. For MOFs, the coordinates of the atoms can be obtained from XRD measurements. The quality of the predicted adsorption results was investigated for pure gas (methane, ethane, propane, nitrogen and carbon dioxide) and gas mixture (methane – carbon dioxide) adsorption on the metal-organic framework CuBTC. The comparison showed a good agreement between experimental and simulated results especially at low pressures. In order to create atomistic models for the mesoporous silica structures that are amorphous on the atomistic level, two existing simulation methods to model MCM-41-type materials were combined: micellar structures from coarse grained simulations that capture the phase separation in the surfactant/silica/solvent mixtures were used as input in kinetic Monte Carlo simulation that created the pore model on the atomistic level. The model created with this new methodology showed similar adsorption behaviour compared with a model created only with the kMC method using an ideal geometrical structure as micelle. The influence of modifications of the MOF structures (exchange of metal, linker length/composition and catenation) was investigated by Grand Canonical Monte Carlo simulations for hydrogen adsorption at low temperature and temperature controlled desorption. The peaks in the desorption spectra could be related to steps in the adsorption isotherms at 20 K.