• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 82
  • 13
  • 5
  • 5
  • 4
  • 4
  • 2
  • 1
  • 1
  • Tagged with
  • 142
  • 142
  • 142
  • 44
  • 31
  • 29
  • 28
  • 27
  • 26
  • 26
  • 26
  • 24
  • 21
  • 16
  • 16
  • 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.
41

Synthesis, Structure And Properties Of Metal-Organic Framework (MOF) Compounds Of 5-Substituted Isophthalic Acids

Sarma, Debajit 05 1900 (has links) (PDF)
Metal organic framework compounds have emerged as an important part of inorganic coordination chemistry during the last two decades. In this thesis, the metal-organic frameworks (MOFs) compounds of 5-substituted isophthalic acids have been investigated. As part of the investigations, preparation of MOF compounds of different 5-substituted isophthalic acids such as 5-aminoisophthalaic acid, 5-nitroisophthalaic acid and 5-sulphoisophthalaic acid have been accomplished. Structures of the newly synthesized compounds were established by single crystal X-ray diffraction technique. Magnetic properties of the transition metal based compounds have been studied by SQUID/PPMS magnetometer. The ligand-sensitized metal-center emission has been studied on the Eu3+ and Tb3+ doped MOF compounds of Y and La. Up-conversion luminescence properties of Nd based compound have also been studied. The labile nature of the coordinated and lattice water molecules was established by employing dynamic in-situ single crystal to single crystal structural transformation studies. In addition, the site selective substitution in homometallic MOF compounds and their subsequent thermal decomposition to mixed-metal spinel oxides have also been investigated. In Chapter 1 of the thesis an overview of the metal-organic framework compounds is presented. In Chapter 2, the synthesis, structure and properties of 5-aminoisophthalate compounds of 3d metals and the rare earth metals are presented. In some of these compounds the coordinate and the lattice water molecules can be removed and reinserted with the retention of single crystallinity. Also some of the isostructural compounds exhibits interesting magnetic behaviors. Partial substitution of the Y3+/La3+ compounds of 5-aminoisophthalate with Eu3+/Tb3+ exhibits characteristics metal centered emission (red = Eu3+ and green = Tb3+). In Chapter 3, the three dimensional compounds of 5-nitroisophthalate and 4, 4’-oxybisbenzoate with cobalt and the high – throughput screening in the synthesis of metal-organic frameworks (MOFs) for the Cu(CH3COO)2.H2O – NIPA – heterocyclic ligand systems are presented. In chapter 4, the single crystal to single crystal transformation with temperature dependent dimensionality cross-over and structural reorganizations in two copper based compounds of 5-sulfoisopphthalate and 5-nitroisophthalate are presented. In chapter 5, the site selective substitution in a homometallic MOF compound and its subsequent decomposition to mixed-metal spinel oxides are presented.
42

Surface organometallic chemistry on Metal Organic Frameworks (MOF) : synthesis, characterization and their application in catalysis / La chimie organométallique de surface appliquée aux structures organométalliques poreuses (MOF) : synthèses, caractérisations, et leurs applications en catalyse

Larabi, Cherif 13 January 2011 (has links)
Les structures organométalliques poreuses (Metal Organic Framework, MOF) sont une nouvelle classe de matériaux, composées d'ions métalliques ou de clusters liés à des ligands organiques ou des complexes organométalliques dans des réseaux cristallins 1D, 2D ou 3D. Au cours de cette thèse la possibilité de construire de nouveaux MOF a été illustrée par le développement de matériaux MOF à base d’imidazolium, précurseur important pour la synthèse de catalyseurs. En outre, ce travail démontre l’utilité de la modification post-synthèse des MOFs par chimie organométallique de surface à visée catalytique : i) un MOF connu, UiO-66, avec des pores relativement petits a été fonctionnalisé avec un groupement amino et ses capacités d'adsorption de gaz ont été étudiées. ii) la synthèse de MOF a structure poreuse, CPO-27, MOF a été optimisée et utilisée comme précurseur pour produire un catalyseur d'hydrodésulfuration après l'introduction d'espèces actives, via la chimie organométallique de surface, dont les performances catalytiques ont été évaluées / Metal organic frameworks (MOF) are a new class of material, which consist of metal ions or clusters coordinated to organic ligands or metal-organic complexes and result in 1D, 2D or 3D crystalline networks. The possibility of constructing new MOF has been exemplified in this thesis by development of imidazolium based MOF, a highly important ligand system in catalysis. Moreover, this work has performed post synthesis modification via surface organometallic chemistry on existing MOF: i) a known MOF, UiO-66, with relatively small pores has been functionalized with amino group and its gas adsorption capacity has been investigated, ii) the syntheses of a 3D open structure MOF, CPO-27, MOFs have been optimized and used as a precursor to produce a hydrodesulfurization catalyst after introducing active species via surface organometallic chemistry approach, whose catalytic performances have been measured
43

Cw and pulsed EPR spectroscopy of Cu(II) and V(IV) in metal-organic framework compounds: metal ion coordination and adsorbate interactions

Jee, Bettina 24 October 2013 (has links) (PDF)
Metal-organic framework (MOF) compounds as a new class of porous coordination polymers consists of metal ions or clusters linked by organic molecules. They have gained recent interest because of their large surface areas and huge variety of the porous network structures. They exhibit interesting adsorption properties and therefore are potential candidates for various technical applications. In this work, continuous wave (cw) and pulsed electron paramagnetic resonance (EPR) methods such as pulsed electron-nuclear double resonance (ENDOR) and hyperfine sublevel correlation (HYSCORE) spectroscopy are applied to study metal-organic frameworks with respect to different aspects of their properties: The host-guest interactions between Cu2+ ions in [Cu3(btc)2]n (HKUST-1; btc: 1,3,5-benzenetricaboxylate) with adsorbed methanol (CH3OH), 13C enriched carbon monoxide and dioxide (13CO, 13CO2), hydrogen (H2), deuterium (D2) and mixed isotopic HD. In [Cu3(btc)2]n, the Cu2+ ions are connected to binuclear Cu/Cu paddle wheel units. Since the Cu2+ ions in the [Cu3(btc)2]n are antiferromagnetically coupled, the new compound [Cu2.97Zn0.03(btc)2]n is synthesized by isomorphous substitution containing about 1 % paramagnetic Cu/Zn paddle wheel units. The modified Cu/Zn paddle wheel units prove to be a very sensitive probe for the interactions with the adsorbed molecules. Secondly, the exchange interactions of antiferromagnetically coupled Cu/Cu paddle wheel units as well as additional inter-paddle wheel exchange interactions between the Cu/Cu pairs are studied in [Cu2(bdc)2(dabco)]n, a layered MOF with 1,4-benzenedicaboxylate (bdc) as linker and 1,4-diazabicyclo[2.2.2]octane (dabco) acting as pillars between the layers. In comparison to [Cu3(btc)2]n, the additional inter-paddle wheel exchange interactions are much easier disturbed by incorporation of Zn2+ ions into the framework structure. Third, the structural dynamics of the framework is investigated in the compound [Al(OH)(bdc)]n (MIL-53) which was isomorphously substituted by V(III)/V(IV) species. The 51V hyperfine structure revealed to be sensitive to the so-called breathing effect, a flexible structural behaviour upon guest adsorption/desorption or upon thermal treatment. It is shown that the aluminum ions can be substituted by vanadium but the octahedral coordination environment changes slightly to a pseudo-octahedral or a square-pyramidal coordination. Based on the hyperfine interactions between the electron spin and the nuclear spins of the surrounding atoms, structural models can be derived from orientation-selective measurements. In such a way, structural information of materials like powder samples and adsorbate complexes can be obtained which are hardly or even not accessible by other methods.
44

Design of isostructural metal-imidazolate frameworks : application for gas storage

Mondal, Suvendu Sekhar January 2013 (has links)
The sharply rising level of atmospheric carbon dioxide resulting from anthropogenic emissions is one of the greatest environmental concerns facing our civilization today. Metal-organic frameworks (MOFs) are a new class of materials that constructed by metal-containing nodes bonded to organic bridging ligands. MOFs could serve as an ideal platform for the development of next generation CO2 capture materials owing to their large capacity for the adsorption of gases and their structural and chemical tunability. The ability to rationally select the framework components is expected to allow the affinity of the internal pore surface toward CO2 to be precisely controlled, facilitating materials properties that are optimized for the specific type of CO2 capture to be performed (post-combustion capture, precombustion capture, or oxy-fuel combustion) and potentially even for the specific power plant in which the capture system is to be installed. For this reason, significant effort has been made in recent years in improving the gas separation performance of MOFs and some studies evaluating the prospects of deploying these materials in real-world CO2 capture systems have begun to emerge. We have developed six new MOFs, denoted as IFPs (IFP-5, -6, -7, -8, -9, -10, IFP = Imidazolate Framework Potsdam) and two hydrogen-bonded molecular building block (MBB, named as 1 and 2 for Zn and Co based, respectively) have been synthesized, characterized and applied for gas storage. The structure of IFP possesses 1D hexagonal channels. Metal centre and the substituent groups of C2 position of the linker protrude into the open channels and determine their accessible diameter. Interestingly, the channel diameters (range : 0.3 to 5.2 Å) for IFP structures are tuned by the metal centre (Zn, Co and Cd) and substituent of C2 position of the imidazolate linker. Moreover hydrogen bonded MBB of 1 and 2 is formed an in situ functionalization of a ligand under solvothermal condition. Two different types of channels are observed for 1 and 2. Materials contain solvent accessible void space. Solvent could be easily removed by under high vacuum. The porous framework has maintained the crystalline integrity even without solvent molecules. N2, H2, CO2 and CH4 gas sorption isotherms were performed. Gas uptake capacities are comparable with other frameworks. Gas uptake capacity is reduced when the channel diameter is narrow. For example, the channel diameter of IFP-5 (channel diameter: 3.8 Å) is slightly lower than that of IFP-1 (channel diameter: 4.2 Å); hence, the gas uptake capacity and Brunauer-Emmett-Teller (BET) surface area are slightly lower than IFP-1. The selectivity does not depend only on the size of the gas components (kinetic diameter: CO2 3.3 Å, N2 3.6 Å and CH4 3.8 ) but also on the polarizability of the surface and of the gas components. IFP-5 and-6 have the potential applications for the separation of CO2 and CH4 from N2-containing gas mixtures and CO2 and CH4 containing gas mixtures. Gas sorption isotherms of IFP-7, -8, -9, -10 exhibited hysteretic behavior due to flexible alkoxy (e.g., methoxy and ethoxy) substituents. Such phenomenon is a kind of gate effects which is rarely observed in microporous MOFs. IFP-7 (Zn-centred) has a flexible methoxy substituent. This is the first example where a flexible methoxy substituent shows the gate opening behavior in a MOF. Presence of methoxy functional group at the hexagonal channels, IFP-7 acted as molecular gate for N2 gas. Due to polar methoxy group and channel walls, wide hysteretic isotherm was observed during gas uptake. The N2 The estimated BET surface area for 1 is 471 m2 g-1 and the Langmuir surface area is 570 m2 g-1. However, such surface area is slightly higher than azolate-based hydrogen-bonded supramolecular assemblies and also comparable and higher than some hydrogen-bonded porous organic molecules. / Metallorganische Gerüstverbindungen (MOFs) sind eine neue Klasse von porösen Koordinationspolymeren, die aus Metall-Knoten und verbrückenden Liganden bestehen. MOFs können Gasgemische trennen und Gase speichern. Aufgrund ihres modularen Aufbaus können die MOF-Eigenschaften systematisch variiert werden. Ein wichtiges Ziel für das Design von MOFs ist die Synthese von Materialien, die eine hohe selektive Aufnahmefähigkeit und -kapazität für Kohlenstoffdioxid besitzen. Im Rahmen der Arbeit ist es gelungen sechs neue MOFs (IFP-5, -6, -7, -8, -9 und -10) zu synthetisieren. Diese MOFs tragen die Kurzbezeichnung IFP. IFP steht als Abkürzung für Imidazolat-Framework-Potsdam (Imidazolat-basierte Gerüstverbindung Potsdam). In diesen IFPs wurde der Metallknoten (Zink, Cobalt, Cadmium) und der Brückenligand, ein 2-substituiertes Imidazolat-amid-imidat, in der Position variiert, um gute und selektive Sorptionseigenschaften für Kohlenstoffdioxid zu erzielen. Von den synthetisierten Verbindungen hat das IFP-5 die besten Sorptionseigenschaften für Kohlenstoffdioxid. Es konnte weiter gezeigt werden, dass sich die IFP-Struktur bei der Wahl von geeigneten Substituenten 2, wie z.B. Methoxy und Ethoxy auch für das Design von gate-opening (Tür-öffnenden) Effekten eignet. Diese Effekte können wiederum genutzt werden, um selektiv Gasmischungen zu trennen. Wenn man das 4,5-Dicyano-2-methoxy-imidazol in Gegenwart von Zink- und Cobalt-Salzen unter solvothermalen Bedingungen zur Reaktion bringt, erhält man beispiellose supramolekulare Wasserstoffbrückenbindungen zu einem dreidimensionalen Netzwerk, die mit Kanälen verknüpft sind. Diese Kanäle können von Lösungsmittelmolekülen (Wasser und Dimethylformamid) befreit werden und Gase aufnehmen. Insgesamt besteht nun die neue MOF-Klasse der Imidazolat-basierten IFPs aus Vertretern. Das Potential der 2-substituierten 4,5-Dicyanoimidazole ist nicht nur auf die Bildung von porösen Koordinationspolymeren beschränkt, sondern kann auch für die Synthese von bisher unbekannten supramolekularen Strukturen genutzt werden.
45

Pillared Paddle-Wheel Frameworks als stationäre Phasen für gaschromatographische Trennungen

Böhle, Tony 20 June 2013 (has links) (PDF)
Metal-organic Frameworks (MOFs) sind eine neue Klasse poröser und kristalliner Feststoffe, die durch ihren modularen Aufbau aus organischen und anorganischen Einheiten einzigartige Eigenschaften unter den porösen Materialien besitzen. Im Mittelpunkt dieser Arbeit steht ihre Anwendung im Bereich der Gaschromatographie, die bislang nur wenig erforscht ist. Dazu werden drei verschiedene MOFs aus der Reihe der „Pillared Paddle-Wheel Frameworks“ (PPFs) in GC Kapillarsäulen abgeschieden und untersucht. Durch systematische Messungen kann gezeigt werden, dass PPFs nicht nur zur Analyse flüchtiger organischer Verbindungen, sondern auch für spezielle Anwendungen wie Größenausschlusschromatographie und Enantiomerentrennungen anwendbar sind. Weiterhin wurden Adsorptionsenthalpien und -entropien sowie Diffusionskonstanten und Massenübergangskoeffizienten für ein breites Analytenspektrum bestimmt.
46

Cw and pulsed EPR spectroscopy of Cu(II) and V(IV) in metal-organic framework compounds: metal ion coordination and adsorbate interactions

Jee, Bettina 25 September 2013 (has links)
Metal-organic framework (MOF) compounds as a new class of porous coordination polymers consists of metal ions or clusters linked by organic molecules. They have gained recent interest because of their large surface areas and huge variety of the porous network structures. They exhibit interesting adsorption properties and therefore are potential candidates for various technical applications. In this work, continuous wave (cw) and pulsed electron paramagnetic resonance (EPR) methods such as pulsed electron-nuclear double resonance (ENDOR) and hyperfine sublevel correlation (HYSCORE) spectroscopy are applied to study metal-organic frameworks with respect to different aspects of their properties: The host-guest interactions between Cu2+ ions in [Cu3(btc)2]n (HKUST-1; btc: 1,3,5-benzenetricaboxylate) with adsorbed methanol (CH3OH), 13C enriched carbon monoxide and dioxide (13CO, 13CO2), hydrogen (H2), deuterium (D2) and mixed isotopic HD. In [Cu3(btc)2]n, the Cu2+ ions are connected to binuclear Cu/Cu paddle wheel units. Since the Cu2+ ions in the [Cu3(btc)2]n are antiferromagnetically coupled, the new compound [Cu2.97Zn0.03(btc)2]n is synthesized by isomorphous substitution containing about 1 % paramagnetic Cu/Zn paddle wheel units. The modified Cu/Zn paddle wheel units prove to be a very sensitive probe for the interactions with the adsorbed molecules. Secondly, the exchange interactions of antiferromagnetically coupled Cu/Cu paddle wheel units as well as additional inter-paddle wheel exchange interactions between the Cu/Cu pairs are studied in [Cu2(bdc)2(dabco)]n, a layered MOF with 1,4-benzenedicaboxylate (bdc) as linker and 1,4-diazabicyclo[2.2.2]octane (dabco) acting as pillars between the layers. In comparison to [Cu3(btc)2]n, the additional inter-paddle wheel exchange interactions are much easier disturbed by incorporation of Zn2+ ions into the framework structure. Third, the structural dynamics of the framework is investigated in the compound [Al(OH)(bdc)]n (MIL-53) which was isomorphously substituted by V(III)/V(IV) species. The 51V hyperfine structure revealed to be sensitive to the so-called breathing effect, a flexible structural behaviour upon guest adsorption/desorption or upon thermal treatment. It is shown that the aluminum ions can be substituted by vanadium but the octahedral coordination environment changes slightly to a pseudo-octahedral or a square-pyramidal coordination. Based on the hyperfine interactions between the electron spin and the nuclear spins of the surrounding atoms, structural models can be derived from orientation-selective measurements. In such a way, structural information of materials like powder samples and adsorbate complexes can be obtained which are hardly or even not accessible by other methods.:1 Introduction 1.1 Electron paramagnetic resonance spectroscopy for investigation of porous materials 1.2 Metal-organic frameworks 1.3 Implementation of paramagnetism by isomorphous substitution 1.4 EPR spectroscopic methods 1.4.1 Spin Hamiltonian 1.4.2 cw EPR spectroscopy 1.4.3 Pulsed EPR spectroscopy 1.5 Description of the project 2 [Cu2.97Zn0.03(btc)2]n 2.1 Introduction: Monometallic [Cu3(btc)2]n (1) 2.1.1 Spin coupling 2.1.2 Adsorption of H2O 2.1.3 Adsorption of DTBN 2.2 Isomorphous substitution of Cu2+ by Zn2+ in [Cu3(btc)2]n 2.2.1 Synthesis and characterisation of [Cu2.97Zn0.03(btc)2]n (2) 2.2.2 cw EPR spectroscopy of 2 2.2.3 Pulsed EPR spectroscopy of 2 2.2.4 Summary: Zn2+ substitution 2.3 Adsorption of methanol (MeOH) on [Cu2.97Zn0.03(btc)2]n (2_MeOH) 2.3.1 cw EPR spectroscopy of 2_MeOH 2.3.2 Pulsed EPR spectroscopy of 2_MeOH 2.3.3 Discussion 2.3.4 Summary: adsorption of MeOH 2.4 Adsorption of 13CO2 and 13CO on [Cu2.97Zn0.03(btc)2]n (2_CO2, 2_CO) 2.4.1 cw EPR spectroscopy of 2_CO2 and 2_CO 2.4.2 Pulsed EPR spectroscopy of 2_CO2 and 2_CO 2.4.3 Discussion 2.4.4 Summary: adsorption of 13CO2 and 13CO 2.5 Adsorption of H2, D2 and HD on [Cu2.97Zn0.03(btc)2]n (2_HH, 2_DD and 2_HD) 2.5.1 cw EPR spectroscopy of 2_HH, 2_DD and 2_HD 2.5.2 Pulsed EPR spectroscopy of 2_HH, 2_DD and 2_HD 2.5.2.1 3p ESEEM spectroscopy of 2_HH, 2_DD and 2_HD 2.5.2.2 Davies-ENDOR spectroscopy of 2_HH 2.5.2.3 Davies-ENDOR spectroscopy of 2_HD 2.5.2.4 Davies-ENDOR spectroscopy of 2_DD 2.5.3 Discussion 2.5.4 Summary: adsorption of H2, D2 and HD 2.6 Conclusion: [Cu2.97Zn0.03(btc)2]n 3 [Cu2(bdc)2(dabco)]n (3) and [Cu(2-x)Zn(x)(bdc)2(dabco)]n (3_x) 3.1 [Cu2(bdc)2(dabco)]n (3) 3.2 [Cu1.9Zn0.1(bdc)2(dabco)]n (3_0.1) 3.3 [Cu(2-x)Zn(x)(bdc)2(dabco)]n (3_0.5, 3_1.0, 3_1.5 and 3_1.9) 3.4 Determination of the exchange coupling constant J 3.5 Discussion 3.6 Conclusions: [Cu(2-x)Zn(x)(bdc)2(dabco)]n (3_x) 4 [(AlOH)1-x(VO)x(bdc)]n (4) and [(AlOH)1-x(VO)x(ndc)]n (5) 4.1 Introduction 4.2 EPR spectroscopic investigations of mixed-metal bdc compounds 4.3 EPR spectroscopic investigations of mixed-metal ndc compounds 4.4: Conclucions: V(III)/V(IV) substitution in [Al(OH)(bdc)]n and [Al(OH)(ndc)]n 5 Summary and Conclusion 5.1 Host-guest interactions 5.2 Exchange couplings of Cu/Cu pairs 5.3 Structural dynamics of the bdc and the ndc framework 5.4 Conclusion 6 Appendix 6.1 Experimental details and additional spectra 6.2 Instrumental details 6.3 Curriculum vitae and publications
47

La chimie organométallique de surface appliquée aux structures organométalliques poreuses (MOF) : synthèses, caractérisations, et leurs applications en catalyse

Larabi, Cherif 13 January 2011 (has links) (PDF)
Les structures organométalliques poreuses (Metal Organic Framework, MOF) sont une nouvelle classe de matériaux, composées d'ions métalliques ou de clusters liés à des ligands organiques ou des complexes organométalliques dans des réseaux cristallins 1D, 2D ou 3D. Au cours de cette thèse la possibilité de construire de nouveaux MOF a été illustrée par le développement de matériaux MOF à base d'imidazolium, précurseur important pour la synthèse de catalyseurs. En outre, ce travail démontre l'utilité de la modification post-synthèse des MOFs par chimie organométallique de surface à visée catalytique : i) un MOF connu, UiO-66, avec des pores relativement petits a été fonctionnalisé avec un groupement amino et ses capacités d'adsorption de gaz ont été étudiées. ii) la synthèse de MOF a structure poreuse, CPO-27, MOF a été optimisée et utilisée comme précurseur pour produire un catalyseur d'hydrodésulfuration après l'introduction d'espèces actives, via la chimie organométallique de surface, dont les performances catalytiques ont été évaluées.
48

Synthesis of Zeolitic Imidazolate Framework-8-Based Nanocomposites and Applications

Zhuang, Jia January 2015 (has links)
Thesis advisor: Chia-Kuang Tsung / Thesis advisor: Eranthie Weerapana / Metal-Organic Frameworks (MOFs) are crystalline porous materials constructed of metal ions and organic linkers, and have been widely utilized in gas storage, sensing, and chromatographic separation. The combination of MOF nanoparticles with other materials will broaden the utilization of MOF materials to a great extent. Several approaches for creating composites with the MOF, Zeolitic Imidazolate Framework-8 (ZIF-8), have been developed: dye and model drug molecules were encapsulated in ZIF-8 pores for potential drug delivery; mesoporous silica monolayer was epitaxially grown on the ZIF-8 surface for structural stability enhancement and hollow structure formation; UiO-66, another MOF subclass, was hierarchically encased inside ZIF-8 for double-phase gas separation and heterogeneous catalysis. By exploring the versatile ZIF-8 platform, these nanocomposites could have great applications in fields such as heterogeneous catalysis and drug delivery. / Thesis (MS) — Boston College, 2015. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.
49

S?ntese e caracteriza??o de Metal-Organic Framework (MOF) para uso na adsor??o de CO2 / Synthesis and characterization of Metal-Organic Framework (MOF) for use in CO2 adsorption

Philippi, Mar?lia 31 August 2017 (has links)
Submitted by PPG Engenharia e Tecnologia de Materiais (engenharia.pg.materiais@pucrs.br) on 2017-10-31T16:39:49Z No. of bitstreams: 1 Disserta??o Final Mar?lia Philippi 2017.pdf: 2898458 bytes, checksum: 0de5c21261331f990e604d9223f1206a (MD5) / Approved for entry into archive by Caroline Xavier (caroline.xavier@pucrs.br) on 2017-11-10T12:35:15Z (GMT) No. of bitstreams: 1 Disserta??o Final Mar?lia Philippi 2017.pdf: 2898458 bytes, checksum: 0de5c21261331f990e604d9223f1206a (MD5) / Made available in DSpace on 2017-11-10T12:41:16Z (GMT). No. of bitstreams: 1 Disserta??o Final Mar?lia Philippi 2017.pdf: 2898458 bytes, checksum: 0de5c21261331f990e604d9223f1206a (MD5) Previous issue date: 2017-08-31 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior - CAPES / Growing concern about global warming and reducing greenhouse gas emissions in the atmosphere has driven the development of technological options to reduce the negative impacts of human activities, and CO2 capture and storage is one of them. Solid adsorbent materials are being used with the aim of adsorbing polluting gases. Metal-Organic Frameworks (MOFs) are a class of porous materials of great potential for adsorption of greenhouse gases, formed by the connection of metallic ions and organic binders. In this context, the objective of this work is to synthesize the MOF of type NH2-MIL-53(Al), to characterize and evaluate its use in the adsorption of carbon dioxide. For synthesis of the MOF, a hydrothermal process was used in a PFA closed reactor (155 ?C) with subsequent washes and resuspensions, obtaining an average mass yield of 90%. The obtained MOF was characterized with the use of the techniques such as SEM-FEG-EDS, elemental analysis, FAAS, XRF, FTIR, TGA, XRD/Refinement by the Rietveld Method and MAS-NMR, exhibiting characteristics of the structure NH2-MIL-53(Al). For the adsorption and desorption tests of CO2 the synthesized material was used as a powder in a fixed bed system. The synthesized MOF presented CO2 adsorption capacity of 0.13 mmol g-1 and SBET of 27 m2 g-1, lower than that reported in the literature, which were attributed to the presence of occluded binder in the pores of the material. The calculated average cost for the synthesis of the MOF in the laboratory was 34% of the value of the non-functionalized commercial standard available in the market. The residual solvent purification process from the MOF synthesis proved to be satisfactory, completely removing the DMF and with a residual contribution of methanol of only 0.00008%. / A crescente preocupa??o com o aquecimento global e com a redu??o das emiss?es de gases de efeito estufa na atmosfera tem impulsionado o desenvolvimento de op??es tecnol?gicas para redu??o dos impactos negativos das atividades humanas e, a captura e armazenamento de CO2 ? uma delas. Materiais s?lidos adsorventes est?o sendo utilizados com o objetivo de adsorver gases poluentes. Os Metal-Organic Frameworks (MOFs) s?o uma classe de materiais porosos de grande potencial para adsor??o de gases de efeito estufa, formados pela conex?o de ?ons met?licos e ligantes org?nicos. Neste contexto, o objetivo deste trabalho ? sintetizar o MOF do tipo NH2-MIL-53(Al), caracterizar e avaliar seu uso na adsor??o de di?xido de carbono. Para s?ntese do MOF foi utilizado processo hidrot?rmico em reator fechado de PFA (155 ?C) com posteriores lavagens e resuspens?es, obtendo um rendimento m?ssico m?dio de 90%. O MOF obtido foi caracterizado com o uso das t?cnicas como MEV-FEG-EDS, an?lise elementar, FAAS, FRX, FTIR, TGA, DRX/Refinamento pelo M?todo Rietveld e MAS-RMN, apresentando caracter?sticas da estrutura NH2-MIL-53(Al). Para os testes de adsor??o e dessor??o de CO2 o material sintetizado foi utilizado sob a forma de p? em sistema de leito fixo. O MOF sintetizado apresentou capacidade de adsor??o de CO2 de 0,13 mmol g-1 e SBET de 27 m2 g-1, inferiores ao reportado pela literatura, e que foram atribu?dos a presen?a de ligante oclu?do nos poros do material. O custo m?dio calculado para s?ntese do MOF em laborat?rio foi de 34% do valor do padr?o comercial n?o funcionalizado dispon?vel no mercado. O processo de purifica??o do solvente residual da s?ntese do MOF demonstrou ser satisfat?rio, removendo completamente o DMF e com uma contribui??o residual de metanol de apenas 0,00008%.
50

Rational Synthesis Toward the Design of Functional Metal-Organic Materials

Eubank, Jarrod F 04 April 2008 (has links)
Design of targeted functional solid-state materials for desired applications remains a scientific challenge. To overcome this hurdle, numerous synthetic strategies have been devised. It has been shown that molecules and/or clusters with pre-selected shapes, molecular building blocks (MBBs), can be utilized as units of chemical construction toward a final structure composed of those units. Typically, in metal-organic structures metal-ligand directed assembly of the MBBs, via coordination chemistry in situ, leads to the final structure. The strength of the MBB formed and, consequently, the overall rigidity of the framework are essential in their use as porous materials for applications. Lack of rigidity, i.e. instability, will ultimately lead to the collapse of the open framework upon evacuation, resulting in inaccessible pores. This phenomenon has been demonstrated repeatedly in labile metal-organic materials (MOMs) constructed via flaccid metal-nitrogen coordination (MNx) between nitrogen-based ligands and metal ions. The structures of simple metal-carboxylate clusters are welldocumented, but only recently have they been targeted for the construction of MOMs. They often possess multiple metal-oxygen coordination bonds (M(CO2)x) that result in the generation of rigid nodes with fixed geometry. Our research group has utilized heterofunctional organic linkers, taking advantage of both pyridine- and carboxylate-based functions (MNy(CO2)z), which has allowed the construction of single-metal-ion-based MBBs resulting in stabile, rigid MOMs with targeted topologies. In this dissertation, I will discuss our single-metal-ion-based design strategy and the utilization of heterofunctional ligands for MNy(CO2)z coordination of single-metal ions. I have employed this strategy to specifically target threeconnected MOMs from 3,5-pyridinedicarboxylate and MNy(CO2)z coordination of various single-metal ions, especially chiral framworks such as (10,3)-a. In addition, I have explored the MOM diversity that can be obtained via various ligand modifications, including isomerism, expansion, and functionalization. I also will show that other heterofunctional ligands can be utilized to target novel MOMs, specifically via M(CO)y(CO2)z coordination, and, resultantly, I have achieved metal-ligand directed organic synthesis and mixed-metal MOMs with magnetic tunability. I have also explored applications for MOMs, including H2 storage, and studied the barriers to rotation of the H2 molecules inside MOMs using inelastic neutron scattering to better understand the MOM-H2 interactions.

Page generated in 0.0498 seconds