• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 71
  • 18
  • 11
  • 9
  • 7
  • 7
  • 6
  • 1
  • 1
  • Tagged with
  • 151
  • 77
  • 75
  • 66
  • 39
  • 38
  • 33
  • 26
  • 26
  • 26
  • 24
  • 21
  • 18
  • 17
  • 17
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
101

Cristallochimie de nouveaux polymères de coordination chiraux poreux à corps central fluorène pour la séparation et la catalyse énantiosélective : synthèses, structures cristallines et réactivité / Cristallochemistry of new chiral coordination polymers with fluorene core for enantioselective separation and catalysis : synthesis, crystal structures and reactivity

Robin, Julien 16 December 2013 (has links)
Ce travail porte sur la cristallochimie de polymères de coordination poreux, ou Metal-Organic Frameworks (MOFs), pour la séparation et la catalyse énantiosélective. Les molécules chirales sont d'une importance capitale et jouent un rôle important dans la reconnaissance moléculaire. Il est donc nécessaire de pouvoir synthétiser un seul énantiomère ou de pouvoir séparer un mélange. La particularité des polymères de coordination à bénéficier d'une partie organique est la possibilité d'introduire des fragments chiraux dans la structure-même des matériaux. Nous avons décidé d'introduire la chiralité dans les MOFs par utilisation de ligands carboxylates originaux chiraux à cœur fluorène. Le premier chapitre de ce mémoire est consacré à l'étude bibliographique des MOFs avec une description des concepts de cette chimie qui permet de comprendre la stratégie mise en place dans cette étude. Le deuxième chapitre décrit la stratégie de synthèse des ligands ainsi que leurs caractérisations. Les trois chapitres suivants décrivent la synthèse, les structures cristallines et les caractérisations physico-chimiques de séries de MOFs regroupés par métal utilisé pour leur élaboration (Zn, Cd et Cu). Ces trois chapitres exposent les problématiques généralement rencontrées avec les MOFs, comme la perte de porosité par interpénétration des réseaux, et les stratégies mises en place pour les contourner, comme l'augmentation de la taille et de la fonctionnalité des ligands utilisés. Enfin la réactivité thermique et chimique des MOFs a été investiguée par diffraction des rayons X par la poudre afin de comprendre les mécanismes réactionnels et la création éventuelle de sites acides en vue d'applications en catalyse. Les techniques expérimentales sont détaillées dans le dernier chapitre de ce mémoire. Enfin un récapitulatif de cette étude est présenté afin de conclure sur la stratégie exposée dans ce mémoire et les perspectives offertes par cette étude. / This work deals with crystallochemistry of new porous coordination polymers or Metal-Organic Frameworks (MOFs) for enantioselective separation and catalysis. Chiral molecules are of a key role in molecular recognition as a consequence the ability to synthesize only one enantiomer or to separate a mixture is priority for chemistry. The particularity of coordination polymers to possess an organic part gives the possibility to introduce chiral fragments in the material structure. We decided to introduce chirality on MOFs by using originals chiral carboxylates ligands with fluorene core. The first chapter is devoted to the bibliographic study of porous coordination polymers. The second chapter describes the ligands synthesis strategy and characterizations. The next three chapters group the crystal structures and physicochemical characterizations of coordination polymers according to the metal used for their preparation (Zn, Cd et Cu). These three chapters explore also the general issues related to MOFs as the loss of porosity consequent to frameworks interpenetration, and strategies implemented to circumvent, such as increasing the size and functionality of the ligands used. Finally the thermal and chemical reactivity of MOFS has been investigated by powder X rays diffraction in order to understand reactions mechanisms and eventually the creation of acid sites for catalytic applications. The experimental technics are detailed in the last chapter. Finally a summary of this work closes this thesis showing the future perspectives of this work.
102

Etude de la dynamique des matériaux poreux hybrides de type MOFs sous l'effet de la pression mécanique / Exploration of the dynamics of hybrid porous materials MOFs under mechanical stimuli

Yang, Ke 07 October 2014 (has links)
Les matériaux hybrides de type MOFs sont des solides poreux dans lesquels des centres métalliques sont reliés entre eux par des ligands organiques. Il est possible, non seulement de faire varier la taille et la géométrie de leurs porosités, mais aussi de moduler leurs compositions chimiques en modifiant à la fois la nature de la brique inorganique et des groupements sur le ligand organique. Cette nouvelle famille de matériaux a fait l'objet d'une attention particulière ces dernières années pour des applications potentielles dans différents domaines à fort intérêt socio-économique comme le captage ou la séparation de gaz ou bien encore la catalyse. Au-delà d'une stabilité chimique et thermique, ces matériaux doivent être aussi suffisamment résistants mécaniquement pour s'adapter au mieux aux contraintes de l'application visée (mise en forme de l'échantillon, conditions opératoires….). Il est donc impératif de connaître les propriétés mécaniques de ces nouveaux matériaux, sujet qui n'a fait l'objet à ce jour que de très peu d'études. L'objectif de ce travail est donc de mettre en œuvre des mesures de diffraction des rayons X et neutrons sur grands instruments afin de caractériser dans un premier temps le comportement structural du matériau flexible MIL-53 (MIL pour Matériaux de l'Institut Lavoisier) sous l'application d'une pression mécanique modérée (P~1 GPa) en fonction de la nature du métal (Al,Cr) et de la fonction greffée sur le ligand organique (-H, -Cl, -CH3). Ces données expérimentales sont ensuite discutées à partir de résultats issus de la simulation moléculaire. L'étape suivante consiste à étudier l'effet du confinement de molécules de solvants dans les pores de ce solide sur la transition structurale du réseau hôte. Enfin, deux familles de MOFs rigides, la MIL-125(Ti) et l'UiO-66(Zr) (UiO pour Unversité d'Oslo) sont considérées afin de caractériser non seulement leur domaine de stabilité mécanique en pression (Pmax~ 5 GPa) mais aussi leur compressibilité. Les résultats ainsi obtenus sont comparés aux performances mécaniques des meilleurs MOFs. / Metal Organic Framework (MOF) materials have been the focus of intense research activities over the past 10 years, with the emergence of a wide range of novel architectures, constructed from inorganic clusters linked by organic moieties. In order to maintain their useful functionalities and high performances in the different fields explored so far (gas storage/separation, catalysis, sensors and many others), besides high chemical and thermal stabilities, MOFs must be also stable enough to resist to different mechanical constraints in both processing and applications. Indeed, there is nowadays a growing interest to characterize the mechanical behaviours of this class of materials under moderate and high applied pressure. This work first aimed to probe the pressure dependence of the structural behaviour of the highly flexible MIL-53 system [MIL stands for Materials of Institut Lavoisier] as a function of the nature of (i) the metal center (Al,Cr) and (ii) the functional group grafted on the organic linker (-H,-Cl,-CH3) using a combination of high-pressure x-ray/neutron diffraction and molecular simulations. The same methodology was further applied to probe how the presence of guest molecules affects the structural transition of this class of hybrid porous solids. Finally, the mechanical stability and the compressibility of two families of rigid MOFs, the MIL-125(Ti) and the UiO-66(Zr) [UiO stands for University of Oslo] up to high pressure (P~5 GPa) have been investigated and their properties in terms of bulk modulus were compared with the most resilient MOFs reported so far.
103

Bildungsbedingungen und rationale Synthesestrategien

Hausdorf, Steffen 18 November 2011 (has links) (PDF)
MOF-5 ist der Archetyp einer neuartigen Klasse hochporöser Materialien, den Metal Organic Frameworks, die unter anderem zur Anwendung als effektive Gasspeicher geeignet sind. Im Rahmen dieser Arbeit werden die seiner Bildung zugrunde liegenden Reaktionen untersucht. Aus den Erkenntnissen dieser Untersuchungen wurden zwei neue Syntheseverfahren entwickelt. Eines der Verfahren beruht auf der Phasenumwandlung von Zinkterephthalaten und ermöglichte die Laborsynthese von MOF-5 in 100 g-Mengen. Ein zweites Verfahren bedient sich des Strukturaufbaus mit Hilfe vorgefertigter anorganischer Cluster, wodurch erstmals die Synthese von MOF-5-Homologen anderer Metalle als Zink gelang.
104

Etude du captage post-combustion du co2 grâce à un procédé vsa (vacuum swing adsorption) avec de nouveaux adsorbants / Study of CO2 post-combustion capture by means of a VSA (Vacuum Swing Adsorption) process with new adsorbents

Guilhamassé, François 09 July 2013 (has links)
Pour faire face à l’augmentation des émissions de CO2 dans l’atmosphère à cause de la production électrique dans des centrales à charbon, le captage en post-combustion au moyen d’un procédé VSA est une solution envisageable. Les adsorbants utilisés dans notre étude sont la TEPA imprégnée sur SiO2, les oxydes de terre rare et le MOF (Metal Organic Frameworks) SIM-1. Pour chaque adsorbant, une étude du perçage puis de la régénération a été effectuée à partir d’une alimentation composée de 15%vol de CO2 et de N2. De ces essais, les conditions opératoires des cycles VSA ont été établies (durées des phases courtes, pas de circulation de purge). En cycle, les performances sont comparées à celle du procédé d’absorption avec la monoéthénolamine. La pureté du désorbat varie de 89,2%vol à 97,2%vol selon les adsorbants et les conditions opératoires. Elle est inférieure à celle du procédé d’absorption (99%vol) mais est correcte pour le transport et le stockage. Le taux de captage évolue de 87,2% à 94,9% (absorption : 98%). La consommation énergétique est inférieure à celle du procédé avec la MEA (de 1,53 à 3,45 MJ.kgCO2 1 pour notre procédé et 3,7 MJ.kgCO2¬1 pour l’absorption) Enfin la productivité est du même ordre de grandeur que celle d’autres procédés VSA de la littérature. Avec le modèle numérique, une étude locale de l’adsorbeur a été menée. Puis grâce à une étude paramétrique, des conditions optimales en cycle ont été déterminées. Les résultats obtenus ont permis de mettre en évidence des performances comparables avec les autres procédés VSA de la littérature. De plus, notre procédé est beaucoup moins énergivore que le procédé d’absorption mais la pureté du désorbat et le taux de captage en CO2 restent inférieurs. / To deal with the CO2 emissions increase in the atmosphere due to electricity production, CO2 post-combustion capture by VSA process is a promising solution. The adsorbents used in this study are impregnated TEPA on SiO2, lanthanide oxides and the MOF (Metal Organic Frameworks) SIM-1. For each adsorbent, a study of breakthrough and regeneration was carried out from a feed composed of 15%vol CO2 and N2. From these experiments, the cyclic operating conditions of VSA have been established (short duration phases, no purge). Cyclic performances are compared to that of the absorption process with monoethenolamine. The desorbate purity varies from 89.2% to 97.2%vol according to adsorbent and operating conditions. It is less than that obtained with absorption process (99%vol) but it is correct for transport and storage. The recovery varies from 87.2% to 94.2% (absorption: 98%). The energy consumption is less than that the process with the MEA (from 1.53 to 3.45 MJ.kgCO2 1 for our process and 3.7 MJ.kgCO2 1 for absorption). . Finally, the productivity is of the same order of magnitude as that of other VSA processes from literature. With the numerical model, a local study of the adsorber was carried out. Afterwards, through a parametric study, cycle optimal conditions were determined. The cycle results highlighted comparable performances with the other VSA processes from literature. Moreover, our process needs less energy than absorption process but the desorbate purity and CO2 recovery remain lower.
105

Síntese de pirazolo[1,5-a]pirimidinas e fluorfenilpirazóis trifluormetilados em ultrassom e síntese e aplicação de [2]rotaxanos / Synthesis of pyrazolo[1,5-a]pyrimidines and fluorophenylpyrazoles trifluoromethylated in ultrasound and synthesis and aplication of [2]rotaxanes

Marzari, Mara Regina Bonini 14 February 2014 (has links)
Conselho Nacional de Desenvolvimento Científico e Tecnológico / This work presents the synthesis of three series of trifluoromethylated heterocycles by using ultrasound irradiation, nomely pyrazolo[1,5-a]pyrimidines, 2,4- difluorophenylpyrazoles and pentafluorophenylpyrazoles. The reactions were performed between trifluoromethylated enones ([CF3C(O)CH=C(R)(OMe], where R = Me, Bu, i-Bu, Ph, 4-MeC6H4, 4-FC6H4, 4-ClC6H4, 4-BrC6H4, 4-IC6H4, thien-2-yl, naphthyl and biphenyl) with three different nucleophiles, nomely (3)(5)-amine-(5)(3)- methylpyrazole, 2,4-difluorophenylhydrazine hydrochloride and pentafluorophenylhydrazine. The trifluoromethylated pyrazolo[1,5-a]pyrimidines were obtained within 5 minutes, giving yields of 61-98 %. The series of 2,4- difluorophenylpyrazoles was obtained in good yields (54-85 %) within 15 minutes by acidifying the reaction medium with PTSA. In the case of the pentafluorophenylpyrazoles, two steps were needed: Firtly the respective 4,5- dihydropentafluorophenylpyrazoles were synthesised and then subsequently submitted to dehydration reactions using PTSA for 15 minutes, giving yields of 54-81 %. The synthesized compounds were identified by 1H and 13C, and by 19F NMR spectroscopy in the some case, mass spectrometry and X-ray diffraction. In some cases homo/heteronuclear spatial interactions involving fluorine atoms have been useful for confirming the identity of the obtained isomer. Another part of this tesis was the synthesis of four mechanically interlocked molecules. Two [2]rotaxanes carrying an ester group in the macrocycle unity were synthesized by using two threads (fumaramide and succinamide derivatives). Once synthesized these [2]rotaxanes were submmited to hydrolysis reactions to give [2]rotaxanes with acid carboxilic group. These macromolecules were synthesized aiming at the formation of MOFs (metal organic frameworks). The synthesis of this compound was carried out by using copper (II) and [2]rotaxane derivative fumaramide. This product was identified by X-ray diffractometry. / Este trabalho apresenta a síntese de três séries de heterociclos trifluorometilados, utilizando irradiação de ultrassom (pirazolo[1,5-a]pirimidinas, 2,4-difluorofenilpirazóis e pentafluorofenilpirazóis). As reações foram realizadas entre enonas trifluorometiladas ([CF3C(O)CH=C(R)(OMe], onde R = Me, Bu, i-Bu, Ph, 4-Me-C6H4, 4-F-C6H4, 4-Cl-C6H4, 4-Br-C6H4, 4-I-C6H4, tien-2-il, bifen-2-il e naftil) e três dinucleófilos diferentes 3-amino-5-metilpirazol, cloridrato de 2,4-difluorofenilhidrazina e pentafluorofenilhidrazina. As pirazolo[1,5-a]pirimidinas trifluorometiladas foram obtidas em 5 minutos de reação com rendimentos de 61-98 %. A série de 2,4- difluorofenilpirazóis foi obtida, acidificando-se o meio de reação com APTS em 15 minutos de reação, e obtendo-se bons rendimentos (54-85 %) no processo. No caso dos pentafluorofenilpirazóis, foram necessárias duas etapas de reação: a primeira a síntese de 4,5-di-idropentafluorofenilpirazóis, e seguida de posterior reação de desidratação utilizando APTS em 15 minutos de reação, obtendo-se produtos com rendimentos de 54-81 %. Após a síntese desses compostos, os mesmos foram identificados por técnicas de RMN de 1H e 13C e de 19F, em alguns casos, espectrometria de massas e difratometria de raios-X. Em alguns casos, através de RMN, foi possível observar interações espaciais do tipo homo/heteronuclear envolvendo átomos de flúor, úteis na confirmação do isômero obtido. Em outra etapa deste trabalho foi desenvolvida a síntese de quatro moléculas mecanicamente entrelaçadas. Foram sintetizados dois [2]rotaxanos com grupamento éster no macrociclo, utilizando dois filamentos lineares (derivados da fumaramida de succinamida). Após a síntese desses [2]rotaxanos, foi realizada a reação de hidrólise dos grupamentos ésteres do macrociclo em grupamento ácidos. Essas macromoléculas foram sintetizadas visando à formação dos MOFs (Redes de metais orgânicas). A síntese desse composto foi realizada utilizando cobre (II) e o [2]rotaxano derivado da fumaramida. Esse produto foi identificado através de difratometria de Raios-X.
106

Ultrathin Two-Dimensional Conjugated Metal-Organic Framework Single-Crystalline Nanosheets Enabled by Surfactant-Assisted Synthesis

Wang, Zhiyong, Wang, Gang, Qi, Haoyuan, Wang, Mao, Wang, Mingchao, Park, SangWook, Wang, Huaping, Yu, Minghao, Kaiser, Ute, Fery, Andreas, Zhou, Shengqiang, Dong, Renhao, Feng, Xinliang 23 October 2020 (has links)
Two-dimensional conjugated metal-organic frameworks (2D c-MOFs) have recently emerged for potential applications in (opto-)electronics, chemiresistive sensing, and energy storage and conversion, due to their excellent electrical conductivity, abundant active sites, and intrinsic porous structures. However, developing ultrathin 2D c-MOF nanosheets (NSs) for facile solution-processing and integration into devices remains a great challenge, mostly due to unscalable synthesis, low yield, limited lateral size and low crystallinity. Here, we report a surfactant-assisted solution synthesis toward ultrathin 2D c-MOF NSs, including HHB-Cu (HHB=hexahydroxybenzene), HHB-Ni and HHTP-Cu (HHTP=2,3,6,7,10,11-hexahydroxytriphenylene). For the first time, we achieve single-crystalline HHB-Cu(Ni) NSs featured with a thickness of 4-5 nm (~8-10 layers) and a lateral size of 0.25-0.65 μm², as well as single-crystalline HHTP-Cu NSs with a thickness of ~5.1±2.6 nm (~10 layers) and a lateral size of 0.002-0.02 μm². Benefiting from the ultrathin feature, the synthetic NSs allow fast ion diffusion and high utilization of active sites. As a proof of concept, when serving as a cathode material for Li-ion storage, HHB-Cu NSs deliver a remarkable rate capability (charge within 3 min) and long-term cycling stability (90% capacity retention after 1000 cycles), superior to the corresponding bulk materials and other reported MOF cathodes.
107

Precise tuning of interlayer electronic coupling in layered conductive metalorganic frameworks

Lu, Yang, Zhang, Yingying, Yang, Chi-Yuan, Revuelta, Sergio, Qi, Haoyuan, Huang, Chuanhui, Jin, Wenlong, Li, Zichao, Vega-Mayoral, Victor, Liu, Yannan, Huang, Xing, Pohl, Darius, Položij, Miroslav, Zhou, Shengqiang, Cánovas, Enrique, Heine, Thomas, Fabiano, Simone, Feng, Xinliang, Dong, Renhao 29 March 2023 (has links)
Two-dimensional conjugated metal-organic frameworks (2D c-MOFs) have attracted increasing interests for (opto)-electronics and spintronics. They generally consist of van der Waals stacked layers and exhibit layer-depended electronic properties. While considerable efforts have been made to regulate the charge transport within a layer, precise control of electronic coupling between layers has not yet been achieved. Herein, we report a strategy to precisely tune interlayer charge transport in 2D c-MOFs via side-chain induced control of the layer spacing. We design hexaiminotriindole ligands allowing programmed functionalization with tailored alkyl chains (HATI_CX, X = 1,3,4; X refers to the carbon numbers of the alkyl chains) for the synthesis of semiconducting Ni3(HATI_CX)2. The layer spacing of these MOFs can be precisely varied from 3.40 to 3.70 Å, leading to widened band gap, suppressed carrier mobilities, and significant improvement of the Seebeck coefficient. With this demonstration, we further achieve a record-high thermoelectric power factor of 68 ± 3 nW m−1 K−2 in Ni3(HATI_C3)2, superior to the reported holes-dominated MOFs.
108

Extending ionothermal synthesis

Aidoudi, Farida Himeur January 2012 (has links)
An exploration of some organic-inorganic hybrid metal fluorides and lanthanide containing metal organic frameworks (Ln-MOFs) has been carried out under ionothermal conditions. In this synthesis technique an ionic liquid (IL) or deep eutectic mixture (DES) is used as the solvent and in many cases as the provider of the organic structure directing agent. A wide range of ILs and DESs have been investigated as the reaction solvent for the synthesis of organically templated vanadium fluorides and oxyfluorides (VOFs), and initially this has proved to be successful with the isolation of 13 phases, including eight new materials. In the VOFs synthesis the IL acts as a solvent, however the DES acts as a solvent and also as a template delivery agent, where the expected template is provided by the partial breakdown of the urea derivative component. Interestingly, it has been shown that the same structure can be accessible via two different ways; either by using IL with an added templating source, or simply through the use of a DES without any other additive; since the template is provided by the in situ breakdown of the DES. The synthesis of VOFs with extended structures was achieved by the use of the hydrophobic IL 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMIM Tf₂N) as the solvent. [HNC₅H₅][V₂O₂F₅] represents the first VOF with a 2D network that contains exclusively V⁴⁺. This material may be considered as arising via condensation of the previously known ladder-like chains. Furthermore, using imidazole as an added template has produced another layer material that has significant similarities to the [HNC₅H₅][V₂O₂F₅] structure, but with some key differences. Within the same system three other phases were also isolated, including two novel materials displaying the known ladder-type building units. Further investigations in the ionothermal synthesis of VOF using EMIM Tf₂N resulted in a successful synthesis of [NH₄]₂[HNC₇H₁₃][V₇O₆F₁₈], a novel material displaying a unique double layered topology featuring a S = ½ kagome type lattice of V⁴⁺ ions (d¹). Two of the V⁴⁺ based kagome sheets are pillared by V³⁺ ions to form a double layered structure templated by both ammonium and quinuclidinium cations. This compound exhibits a high degree of magnetic frustration, with significant antiferromagnetic interactions but no long range ordering was observed above 2 K. This material presents an interesting comparison to the famous Herbertsmithite, ZnCu₃(OH)₆Cl₂, and may provide an excellent candidate for realising a quantum spin liquid (QSL) ground state. Interestingly, in this system the use of EMIM Tf₂2N as a solvent produces mainly V⁴⁺-containing materials, despite the high reaction temperature (170 °C). This characteristic is unprecedented in VOFs synthesis, as rising the reaction temperature above 150 °C in other techniques (i.e. hydrothermal synthesis) would often result in further reduction of V⁴⁺ to V³⁺. Using the ionothermal technique in the synthesis of hybrid iron fluorides resulted in the isolation of three chain-type materials. Again, the IL acts as the solvent and the DES acts as the solvent and also as the template provider where the expected template is released by the partial breakdown of the urea derivative component of the DES. The synthesis of Ln-MOF using a choline chloride/ 1,3-dimethylurea deep eutectic mixture has produced three novel isostructural materials. Usually, in ionothermally prepared materials (i.e. zeolites) the urea portion of the DES is unstable and breaks down in situ to form ammonium or alkylammonium cations. In the ionothermal synthesis of Ln-MOF, 1,3-dimethyurea (DMU) remains intact and is occluded in the final structure. Using a choline chloride/ethylene glycol deep eutectic solvent led to the isolation of a Ln-MOF with interesting structural properties, however none of the DES components appeared in the final structure. These results demonstrate once more the usefulness and applicability of the ionothermal synthesis method and emphasise how this synthesis technique can be further extended and applied in the preparation of important structures with unique properties and functionalities.
109

Teoretické studium vlastností 3D a 2D zeolitů / Theoretical Investigation of Properties of 3D and 2D Zeolites

Ho, Viet Thang January 2016 (has links)
Zeolites have been widely used in many different fields including catalysis, adsorption and separation, ion exchange, or gas storage. Conventional zeolites have three- dimensional (3D) structures with microporous channel system; typical pore sizes are well below 1 nanometer, therefore, diffusion limitation plays important role in many process and bulkier reactants (or products) cannot enter (or leave) the zeolite channel system. Two-dimensional (2D) zeolites prepared in last years can lift all diffusion limitation and they thus offer a very attractive alternative to conventional 3D zeolites. 2D zeolites attracted considerable attention on the experimental side; however, understanding of 2D zeolites based on computational investigation or on a combination of experimental and computational investigation is limited. A motivation for the computational work presented here is to improve our understanding of properties of 2D zeolites based on computational investigation. The originality of the research presented herein is in the strategy: we carried out systematic investigation of properties of corresponding 2D and 3D zeolites and we focus on the identification of similarities and differences. The most important zeolite properties, i.e., presence of Brønsted and Lewis acid sites, are investigated. A number of...
110

Mixed matrix membranes comprising metal organic frameworks and high free volume polymers for gas separations

Khdhayyer, Muhanned January 2017 (has links)
This research aimed to develop new composite membranes using a polymer of intrinsic microporosity (PIM-1) and metal organic frameworks (MOFs) for use in gas separations. PIM-1 was successfully synthesised using the high temperature method (40 min, 160 oC) and the resulting polymer was cast into membranes. PIM-1 membranes were chemically modified by reacting hexamethylenediamine (HMDA) with the nitrile group of PIM-1 to form HMDA-modified PIM-1 membranes. Surfaces of PIM-1 membranes were also modified by basic hydrolysis to form amide-modified PIM-1 membranes. These polymer materials were characterized by different techniques (GPC, NMR, ATR-IR, TGA, Elemental analysis and nitrogen sorption analysis). In addition, eight MOF materials [MIL-101(Cr), ED-g-MIL-101(Cr), TEPA-g-MIL-101(Cr), MIL-101(Cr)-NH2, MIL-101(Al)-NH2, UiO-66(Zr), UiO-66-NH2 and UiO-66(COOH)2] were successfully synthesized. They were chosen due to having high surface areas and large porosity. These MOF compounds were characterized using PXRD, SEM, TGA, and low pressure N2.Successful PIM-1/MOF MMMs were fabricated utilising PIM-1 and the MOFs outlined above with various loadings. The highest MOF loading achieved was 28.6 wt. %, apart from MIL-101(Cr)-NH2, for which it was 23.1 wt. %, and MIL-101(Al)-NH2, for which it was 19.8 wt. %. The morphology of MMMs was characterized by scanning electron microscopy (SEM), proving the dispersion of MOF fillers. Novel PIM-1 supported MOF membranes were successfully prepared by depositing ZIF-8 and HKUST-1 layers on the surfaces of unmodified and modified PIM-1 membranes. These materials were characterized using PXRD, SEM, ATR-IR and SEM-EDX. Gas permeation properties of the MOF/PIM-1 MMMs and PIM-1 supported MOF membranes were determined using a time lag method. Most MMMs tested showed an increase in the permeability and stable selectivity as the MOF amount was increased. However, this was not true for MIL-101(Al)-NH2, where the permeability and selectivity decreased. In contrast, PIM-1 supported ZIF-8 and HKUST-1 membranes caused a sharp decrease in the permeability and increase in the selectivity.

Page generated in 0.0509 seconds