[ES] Se han preparado varios materiales metal orgánicos de circonio MOF-808 para evaluar sus propiedades catalíticas en reacciones tipo Meerwein-Ponndorf-Verley (MPV) para la reducción de compuestos carbonílicos. En particular, se han sintetizado compuestos tipo MOF-808 modificados en los que una pequeña fracción de los ligandos trimesato presentes en el MOF original se ha reemplazado por ligandos dicarboxilato, como una estrategia para inducir la creación controlada de defectos estructurales. Los ligandos utilizados han sido: isoftalato (MOF-808-IPA), 3,5-piridindicarboxilato (MOF-808-Pydc), 5- aminoisoftalato (MOF-808-NH2) y 5-hidroxiisoftalato (MOF-808-OH). Todos los materiales obtenidos presentan una elevada cristalinidad y son isoreticulares respecto al MOF-808 original. Se ha evaluado la actividad catalítica del MOF-808 original y de los materiales modificados en reacciones tipo MPV, utilizando ciclohexanona como compuesto modelo. Todos los materiales presentan una elevada actividad catalítica, superior a la del tereftalato de circonio UiO-66 utilizado como referencia. Esta mayor actividad catalítica se corresponde a un mayor número de iones Zr4+ con insaturación coordinativa presentes en el MOF-808 con respecto al UiO-66. Además, los materiales MOF-808-IPA y MOF-808-Pydc presentan una mayor actividad que el MOF-808 original, lo que se debe a la presencia de centros activos menos congestionados estéricamente debido a la introducción de los ligandos dicarboxilato. Una ventaja adicional de compuestos MOF-808 con respecto al UiO-66 es su sistema de poros más grande, lo que permite la conversión de moléculas de mayor tamaño. Para evaluar esta característica, se ha utilizado un compuesto de gran tamaño, la estrona, capaz de penetrar en los poros del MOF-808 pero no en el UiO-66. En consecuencia, el MOF-808 es capaz de convertir por completo la estrona de forma selectiva a estradiol, mientras que el UiO-66 apenas presenta actividad. Además, cuando se usa el MOF-808 como catalizador, se produce una cantidad considerable del isómero 17alfa-estradiol, difícil de obtener por otros medios, por lo que las propiedades de diastereoselectividad del MOF-808 en reacciones MPV resultan de gran interés preparativo. Con el fin de estudiar en mayor detalle la diastereoselectividad de reacciones MPV catalizadas por MOF-808, se ha estudiado la reducción de ciclohexanonas substituidas: 3-metilciclohexanona (3MeCH), 2-metilciclohexanona (2MeCH) y 2-fenil-ciclohexanona (2PhCH). En función del alcohol utilizado como reductor y de la posición del grupo substituyente en la ciclohexanona, el MOF-808 favorece selectivamente la formación de uno u otro isómero, con una diastereoselectividad variable: 82%, 61% y 94%, respectivamente para 3MeCH, 2MeCH y 2PhCH. Es posible racionalizar estos resultados considerando la formación preferencial de uno u otro estado de transición en el espacio confinado disponible dentro de los poros del MOF. Las características energéticas del proceso se han analizado mediante el uso combinado de estudios cinéticos y cálculos teóricos. Finalmente, en vista las interesantes propiedades del MOF-808 como catalizador para reacciones MPV, se ha extendido con éxito el uso de este material a la preparación de compuestos hidroxiesteroides de difícil obtención y de interés farmacológico mediante la reducción quimio-, regioy diastereoselectiva del correspondiente oxoesteroide. De esta forma, se han conseguido obtener en un solo paso de reacción y con una elevada selectividad los siguientes compuestos: 17alfa-estradiol, 5alfa- androstan-3beta,17alfa-diol y epitestosterona, lo que demuestra el potencial del MOF-808 como catalizador para la síntesis de compuestos de alto valor añadido. / [CA] S'han preparat varis materials metall orgànics de zirconi MOF-808 per avaluar les seves propietats catalítiques en reaccions tipus Meerwein-Ponndorf-Verley (MPV) per a la reducció de composts carbonílics. En particular, s'han sintetitzat composts tipus MOF-808 modificats en els que una petita fracció dels lligands trimesat presents en el MOF original s'han reemplaçat per lligands dicarboxilats, com una estratègia per induir la creació controlada de defectes estructurals. Els lligands utilitzats han sigut: isoftalat (MOF-808-IPA), 3,5-piridindicarboxilat (MOF-808-Pydc), 5-aminoisoftlatat (MOF-808- NH2) i 5-hidroxiisoftalat (MOF-808-OH). Tots els materials preparats presenten una elevada cristal·linitat i són isoreticular respecte al MOF-808 original. S'ha avaluat l'activitat catalític del MOF-808 original i dels materials modificats en reaccions tipus MPV, utilitzant ciclohexanona com a compost model. Tots els materials presenten una elevada activitat catalítica, superior a la del tereftalat de zirconi UiO-66 utilitzat com a referència. Aquesta major activitat catalítica es correspon a un major nombre d'ions Zr4+ amb insaturació coordinativa presents en el MOF-808 respecte a l'UiO-66. A més, els materials MOF-808-IPA i MOF-808-Pydc presenten una major activitat que el MOF-808 original, el que és debut a la presència de centres actius menys congestionats estèricament debut a la introducció dels lligands dicarboxilat. Un avantatge addicional dels MOF-808 respecte a l'UiO-66 és el seu sistema de porus més gran, que permet la conversió de molècules de major tamany. Per avaluar aquesta característica, s'ha utilitzat un compost de gran taman, l'estrona, capaç de penetrar en els porus del MOF-808 però no en els de l'UiO-66. En conseqüència, el MOF-808 és capaç de convertir completament l'estrona de forma sel·lectiva a l'estradiol, mentre que l'UiO-66 gairebé no presenta activitat catalítica. A més, quan s'usa el MOF- 808 com a catalitzador, es produeix una quantitat considerable de l'isòmer 17alfa-estradiol, difícil d'obtenir per altre medis, de manera que les propietats de diastereoselectivitat del MOF-808 en reaccions MPV resulten de gran interès preparatiu. Per tal d'estudiar en major detall la diastereoselectivitat de reaccions MPV catalitzades per MOF-808, s'ha estudiat la reducció de ciclohexanones substituïdes: 3-metilciclohexanona (3MeCH), 2- metilciclohexanona (2MeCH) i 2-fenil-ciclohexanona (2PhCH). En funció de l'alcohol usat com a reductor i de la posició del grup substituent en la ciclohexanona, el MOF-808 afavoreix selectivament la formació d'un o de l'altre isòmer, amb una diastereoselectivitat variable: 82%, 61% y 94%, respectivament per a 3MeCH, 2MeCH y 2PhCH. És possible racionalitzar aquest resultats considerant la formació preferent d'un o l'altre estat de transició en l'espai confinat disponible dins dels porus del MOF. Les característiques energètiques del procés s'han analitzat mitjançant l'ús combinat d'estudis cinètics i càlculs teòrics. Finalment, en vista de les interessants propietats del MOF-808 com a catalitzador per a reaccions MPV, s'ha estès amb èxit l'ús d'aquest material a la preparació de composts hidroxiesteroids de difícil obtenció i d'interès farmacològic mitjançant la reducció quimio-, regio- i diastereoselectiva del corresponent oxoesteroid. D'aquesta manera, s'ha aconseguit obtenir en un únic pas de reacció i amb una elevada selectivitat els següents composts: 17alfa-estradiol, 5alfa-androstan-3beta,17alfa-diol i epitestosterona, el que demostra el potencial del MOF-808 com a catalitzador per a la síntesi de composts d'alt valor afegit. / [EN] Various zirconium-containing MOF-808 compounds have been prepared as potential catalysts for the Meerwein-Ponndorf-Verley (MPV) reduction of carbonyl compounds. Modified MOF-808 have been synthethized in which a small fraction of the trimesate ligands present in pristine MOF-808 has been replaced by dicarboxylate ligands, as a strategy to induce a controlled creation of defects. The linkers used are: isophthalate (MOF-808-IPA), 3,5-pyridinedicarboxylate (MOF-808-Pydc), 5-aminoisophthalate (MOF-808-NH2) and 5-hydroxyisophthalate (MOF-808-OH). All these compounds are highly crystalline and isoreticular with pristine MOF-808. The catalytic activity of pristine and defect engineered MOF-808 has been evaluated for MPV reactions, using cyclohexanone as model substrate. All the materials show a higher catalytic activity than that of zirconium terephthalate UiO-66 used as reference. This higher activity is attributed to the higher amount of coordinatively unsaturated Zr4+ ions in MOF-808 than in UiO-66. Moreover, MOF- 808-IPA and MOF-808-Pydc are more active than pristine MOF-808, which is due to the creation of less sterically crowded sites due to the introduction of defective dicarboyxlate linkers. A further advantage of MOF-808 over UiO-66 is the presence of a wider pore system, which allows converting bulkier substrates. To evaluate this characteristic, a bulky ketone has been used; estrone, which can enter the pores of MOF-808 but not those of UiO-66. Accordingly, MOF-808 can fully convert estrone selectively to estradiol, while UiO-66 shows barely any catalytic activity. Interestingly, when MOF- 808 is used as catalysts, a noticeable amount of the isomer 17alpha-estradiol is produced, which is difficult to obtain by other means. Therefore, the diastereoselective properties of MOF-808 for MPV reactions are interesting from the preparative point of view. In order to investigate in more detail the diastereoselective properties of MOF-808 for MPV reactions, various substituted cyclohexanones have been considered: 3-methylcyclohexanone (3MeCH), 2- methylcyclohexanone (2MeCH) and 2-phenylcyclohexanone (2PhCH). Depending on the alcohol used as reducing agent and the position of the substituent in the cyclohexanone molecule, MOF-808 selectively favors the formation of one isomer or the other with a different diastereoselectivity: 82%, 61% and 94%, respectively for 3MeCH, 2MeCH y 2PhCH. These results can be rationalized by considering the preferential formation of a given transition state in the confined space available inside the MOF pores. The energetic characteristics of the process have been analyzed by a combined use of kinetic studies and theoretical calculations. Finally, in view of the interesting properties of MOF-808 as catalyst for MPV reactions, this material has been successfully applied to the preparation of a number of challenging hydroxysteroid compounds with pharmacologic interest through a chemo-, regio- and diastereoselective reduction of the corresponding oxosteroid. In this way, it has been possible to prepare in one single reaction step the following compounds: 17alpha-estradiol, 5alpha-androstan-3beta,17alpha-diol and epitestosterone. This demonstrates the high potential of MOF-808 as a catalysts for the synthesis of high added value compounds. / I want to thank the European Union’s Horizon 2020 research and innovation program for a contract under the Marie Sklodowska-Curie grant agreement No. 641887 (Project acronym: DEFNET). / Mautschke, H. (2019). Zirconium Metal Organic Frameworks as Heterogeneous Catalysts for Meerwein-Ponndorf-Verley Reactions [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/130203 / TESIS

Tuning the surface structure at the atomic level is of primary importance to simultaneously meet the electrocatalytic performance and stability criteria required for the development of low-temperature proton-exchange membrane fuel cells (PEMFCs). However, transposing the knowledge acquired on extended, model surfaces to practical nanomaterials remains highly challenging. Here, we propose the ‘Surface Distortion’ as a novel structural descriptor, which is able to reconciliate and unify seemingly opposing notions and contradictory experimental observations in regards to the electrocatalytic oxygen reduction reaction (ORR) reactivity. Beyond its unifying character, we show that surface distortion is pivotal to rationalise the electrocatalytic properties of state-of-art of PtNi/C nanocatalysts with distinct atomic composition, size, shape and degree of surface defectiveness under simulated PEMFC cathode environment. Our study brings fundamental and practical insights into the role of surface defects in electrocatalysis and thus highlights strategies to design more efficient and durable new generation of nanocatalysts

Abstract: Superacidic mesoporous silica materials containing embedded heteropolyacids (HPAs) were synthesized by sol–gel method in acidic media. In these materials, HPAs were immobilized into the silica structure covalently. The most acidic materials were obtained at the use of Pluronic P123 as a non-ionic pore-forming agent. Ionic surfactants also formed mesoporous structures, however, their interaction with HPA reduced acidity of the products. Obtained materials were tested as heterogeneous catalysts in liquid-phase alkylation of 1,3,5-trimethylbenzene by 1-decene. The most effective catalyst demonstrated higher conversion of starting substances to long-chain isomeric alkylbenzenes as compared to the activity of zeolite HY, a well-known alkylation catalyst. No leaching of HPA from silica gel was observed after the alkylation.

Thesis (DTech (Chemistry))--Cape Peninsula University of Technology, 2016. / The use of ozone as an advanced oxidation process is gathering wide spread attention with the major limitation to its application being its cost of operation and design considerations. While the general approach of most researches is to buttress the already known fact of the efficacy of the process, little attention is given to studying the by-products of ozone reactions with organics. The aims of this study were to investigate the efficacy of the ozonation process for removing recalcitrant phenolics: phenol, 2-chlorophenol (2CP), 4-chlorophenol (4CP) and 2,4-dichloropheno (2,4DCP) from aqueous medium with a view of understanding various reaction pathways of the process and identifying possible intermediates and residual compounds using liquid chromatography-mass spectrometry (LC-MS). The choice of the selected chlorophenols would also elucidate the role of the positioning of the chlorine atoms in determining reaction rates, pathways and subsequent mechanisms and by-products. Sequel to this, oxy-hydroxy iron in β-phase (β-FeOOH, akaganite) and various β-FeOOH bonded composites on support metal oxides (Al2O3, NiO and TiO2) were prepared via hetero-junction joining, and explored as a possible promoter to improve the efficiency of the ozonation process. Apparent first order reaction rates constants of tested phenolics was in the order 2,4-DCP > 2-CP > Phenol > 4-CP, irrespective of the tested pH. The individual rates however increased with increasing pH. The position 4 chlorine atom was found to be least susceptible to hydroxylative dechlorination. Catechol intermediate and pathway was identified as the major degradation pathway for phenol and 2-CP, while 4-chlorocatechol pathways were more important for 4-CP and 2,4-DCP. The formation of polymeric dimers and trimers by all compounds was pronounced at alkaline pH. Heterogeneous catalytic ozonation using β-FeOOH reduced ozonation time for 4-CP by 32%. Mechanism for β-FeOOH/ozone catalysis showed that the catalyst suffered reductive dissolution in acidic pH and the kinetics of 4-CP removal using the catalyst was best described using a two stage kinetic model. The first stage was attributed to heterogeneous catalysis of ozone breakdown on β-FeOOH surface generating faster reacting radicals, while the second stage was due to homogeneous catalysis by reduced Fe2+ ions in solution. β-FeOOH stabilized on NiO at a 5% ratio exhibited superior catalytic property compared to the other tested composites. Characterization by high-resolution transmission electron microscopy (HRTEM) affirmed a β-FeOOH-NiO bonded interfaced composite which was stable as a iv catalyst over four (4) recycle runs. The mechanism of operation of the composite was via an increased ozone breakdown to radicals as monitored via photoluminescence experiments. The composite material produced satisfactory results when tested on real wastewater samples. Results from this study contribute to the current understanding on reaction mechanisms for ozone with phenols and chlorophenols, for the first time monitoring time captured intermediates via liquid chromatography-mass spectrometric method, which preserves the integrity of reaction intermediates. Also this study proposes heterogeneous catalysts; β-FeOOH and β-FeOOH bonded composites as possible improvements for simple ozone based water purification systems.

The general objective of this thesis is the analysis of selective reactions for group VI grafted metal complexes via methods and principles of SOMC. For this objective, three approaches have been chosen. The first chapter is an introduction to the topic of selectivity in catalysis, emphasizing heterogeneous catalysis and more specifically the different approaches to support catalysts on surfaces. The concept of catalysis by design is introduced as a new way to use the surface as a ligand. Chapter 2 presents the results of a library of well-defined catalysts of group VI with identical catalytic functionality, but different ligand environment. The results reveal, that metal-carbynes are able to switch their catalytic reactivity based on the substrate that they are contacted with. The difference in reaction mechanisms and the differing reactivities towards the substrates are presented. It can be concluded that the classical ROMP is selectively achieved with cyclic alkene substrates leading to polymers whereas cyclic alkanes yield exclusively higher and lower homologues of the substrate without polymeric products. Chapter 3 presents the study of olefin metathesis of cis-2-pentene with metal-carbynes of group VI, where the selectivity of the catalyst library towards yield of cis-/trans products is analyzed. It is presented, that the ligand environment of the catalysts is showing an influence in the selectivity. Rates of cis/trans isomerization of the products are high and are approaching thermodynamic equilibrium at high conversion. Product isomerization, thermodynamic equilibrium and reactivity differences between liquid phase and gas phase products are analyzed. Chapter 4 presents the full characterization of tungsten-hydrides by selective transformation into tungsten-hydroxides. These newly discovered well-defined tungstenhydroxides are fully characterized by ICP, TEM, DRIFT, double quantum and triple quantum solid-state NMR. The presented results allow to predict that tungsten-hydrides on KCC-1700 are present as two distinct species. Catalysis results with cyclooctane show, that due to burial of the complexes in the KCC-1700 surface the tungsten-hydrides are less active towards cyclic alkane metathesis reactions with bulky cyclooctane than the metalcarbyne complexes. Chapter 5 is giving a conclusion of results and an outlook for catalytic applications of the generated tungsten-hydroxides of chapter 4.

Since our society became industrialised, the levels of carbon dioxide in our atmosphere have been steadily rising, to the point where it in early 2020 at is 413 ppm. The high concentration is causing several troubling effects worldwide because of the increase in mean temperature that it creates, which causes longer draughts, more severe floods, and rising seawater levels to name a few. There are a few measures that can be taken to reduce carbon dioxide in the atmosphere, among which there are a number of methods that currently are being researched and/or used. The prospect of capturing carbon dioxide and using it as a carbon building block to make methanol is one solution that is particularly interesting, since it in theory could provide a fuel for combustion engines that is net neutral regarding carbon emission. Methanol can be synthesised from carbon dioxide using a heterogeneous catalyst consisting of copper, Cu, and zinc oxide, ZnO. This research is focused on one of the components of the catalyst, the metal oxide ZnO in the form of crystallites or nanoparticles (ZnO)n. Quantum chemistry is a branch of computational chemistry which is centered on solving the Schrödinger equation for molecular systems. Density functional theory, DFT, is an approach to quantum theory which in this study was used to calculate the geometry and energy of the particles. The supercomputer Tetralith in the National Supercomputer Centre, NSC, was used to carry out the calculations. The DFT calculations utilized the functional B3LYP and the basis set 6-31G (d,p). One of the largest particle sizes studied, (ZnO)20, with a structure that has a large, flat surface, was found to be the most energetically favourable. According to studies, the presence of an oxygen vacancy on the surface of ZnO reduces the amount of activation energy required for CO2 to bond to the particle, which increases the chance of forming CO and thus continuing the process of forming methanol. Two structures of (ZnO)20 were investigated in this regard, where oxygen atoms were removed at different locations, creating four versions of Zn20O19 in total. This proved yet again that the version with a large, flat surface yields the lesser amount of energy when an O atom is removed from the centre of its surface. The adsorption of CO2 to the ZnO clusters was studied by calculating the energy of adsorption, and this showed that it was the second version of (ZnO)20, without an O vacancy, that yielded the least amount of energy, thus being the most favourable species to engage in physisorption with CO2. Lastly, the activation energy was investigated, and a diagram of the reaction process of CO2 adsorbing to Zn20O19 forming (ZnO)20 and CO is presented in this paper, which shows that the required activation energy is 127 kJ/mol.

京都大学 / 0048 / 新制・論文博士 / 博士(工学) / 乙第12931号 / 論工博第4124号 / 新制||工||1626(附属図書館) / 32141 / (主査)教授 北川 進, 教授 杉野目 道紀, 教授 濵地 格 / 学位規則第4条第2項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DGAM

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This thesis focuses on the study of nickel boride as a catalyst in various coupling reactions. The nickel boride catalyst was investigated in three different coupling reactions, the experiments aimed at understanding the activity and catalytic properties of nickel boride. We successfully synthetized the nickel boride catalyst, alongside with the cobalt and iron boride. Different methods of preparation were compared and we concluded, that the differences in the preparation, such as solvent and atmosphere, influence the activity of the catalyst in coupling reactions. We found that the most suitable solvent for preparing nickel boride is anhydrous methanol, thus we proceeded our research with this catalyst. In the case of the Sonogashira cross-coupling we found that the homocoupling of the acetylene starting material is a side reaction we could not exclude. However, with the proper solvent it is possible to shift the reaction towards homocoupling, without the formation of the heterocoupling product. Thus, we decided to investigate the Glaser homocoupling between acetylenes. In the case of the Sonogashira coupling only TLC was used to examine the reaction mixture. However, in the case of Glaser coupling, after pre-investigations we developed a gas chromatography method for analyzing the reaction mixtures. We learned, that the homocoupling only results in trace amounts (2-4%) of product. Previous investigations in our research group showed, that the nickel boride could catalyze Suzuki-Miyaura-type couplings. Examining this reaction all three metal borides were tested; however, the reactions only led to the desired product with nickel boride. Analyzing the reaction with gas chromatography we learned that the choice of solvent influences the stability of the starting materials and the formation of side products. Reactions with different starting materials, in different solvents, with different bases were analyzed. The effect of microwave irradiation was also examined. Based on the results we concluded, that with nickel boride it is not possible to achieve high yields in coupling reactions.