Academic literature on the topic 'Colloidal MOFs'

Colloidal dye-sensitized photocatalysis is a promising route toward efficient solar fuel production by merging properties of catalysis, support, light absorption, and electron mediation in one. Metal-organic frameworks (MOFs) are host materials with modular building principles allowing scaffold property tailoring. Herein, we combine these two fields and compare porous Zr-based MOFs UiO-66-NH2(Zr) and UiO-66(Zr) to monoclinic ZrO2 as model colloid hosts with co-immobilized molecular carbon dioxide reduction photocatalyst fac-ReBr(CO)3(4,4′-dcbpy) (dcbpy = dicarboxy-2,2′-bipyridine) and photosensitizer Ru(bpy)2(5,5′-dcbpy)Cl2 (bpy = 2,2′-bipyridine). These host-guest systems demonstrate selective CO2-to-CO reduction in acetonitrile in presence of an electron donor under visible light irradiation, with turnover numbers (TONs) increasing from ZrO2, to UiO-66, and to UiO-66-NH2 in turn. This is attributed to MOF hosts facilitating electron hopping and enhanced CO2 uptake due to their innate porosity. Both of these phenomena are pronounced for UiO-66-NH2(Zr), yielding TONs of 450 which are 2.5 times higher than under MOF-free homogeneous conditions, highlighting synergistic effects between supramolecular photosystem components in dye-sensitized MOFs.

Recently, metal-organic frameworks (MOFs) have garnered enormous attention from researchers owing to their superior physicochemical properties, which are of particular interest in various fields such as catalysis and the diverse areas of biomedicine. Despite their position in the utilization for various applications compared to other innovative nanocarriers such as dendrimers and mesoporous silica nanoparticles (MSNs), in terms of advantageous physicochemical attributes, as well as attractive textural properties, ease of characterization, and abundant surface chemistry for functionalization and other benefits, MOFs yet suffer from several issues such as poor degradability, which might lead to accumulation-induced biocompatibility risk. In addition, some of the MOFs suffer from a shortcoming of poor colloidal stability in the aqueous solution, hindering their applicability in diverse biomedical fields. To address these limitations, several advancements have been made to fabricate polymeric nanocomposites of MOFs for their utility in various biomedical fields. In this review, we aim to provide a brief emphasis on various organic polymers used for coating over MOFs to improve their physicochemical attributes considering a series of recently reported intriguing studies. Finally, we summarize with perspectives.

ABSTRACTMetallic silver nanoparticles (NPs) have extensively been used in the treatment of disease and purification and heralded the ‘first wave’ of disinfection science, the ‘second wave’ being the nanocomposite of metal-doped TiO2. Recent advances in engineered surfaces have enabled ultrahigh surface area and rapid sterilization via using metal-organic frameworks (MOFs) as the ‘third wave’ disinfectant. MOFs offer the same advantages as colloids but also have ultra high surface area, long term persistence and ultra low doses, applied for water purification.

Esta Tesis tiene como objetivo dar al lector una idea sobre las nuevas perspectivas abiertas en la manipulación controlada de Metal-Organic Frameworks con precisión nanométrica y sus consecuencias en las propiedades finales y aplicaciones. El presente estudio se propone crear un puente entre MOFs y Nanotecnología; es decir, enlazar las propiedades clásicas de los MOFs con nuevas funcionalidades que pueden emerger gracias a la manipulación a la nanoescala. Este puente entre los dos campos se ha llevado a cabo con un MOF icónico, llamado Zeolitic-Imidazolate Framework-8 (ZIF-8), uno de los MOFs más estudiados, debido su fácil síntesis su alta porosidad y gran estabilidad térmica, química y hidrolítica. La Tesis está organizada en dos partes. En el primer capítulo, que corresponde a la primera parte, el lector encontrará una introducción al concepto de la porosidad con ejemplos de materiales porosos naturales. Este capítulo continua con una breve presentación de los MOFs y una extensa introducción al ZIF-8. A través de ejemplos y conceptos especialmente seleccionados, esta introducción trata de captar la atención del lector en el principal argumento de la presente tesis, la manipulación de los MOFs a la nanoescala con el objetivo de ir más allá de sus propiedades clásicas. La segunda parte de la tesis se inicia con la descripción de los objetivos en el Capítulo 2. Los capítulos 3, 4 y 5 incluyen cada una, una publicación relacionada con la manipulación de MOFs a la nanoescala, usando el ZIF-8 y –en otros casos- otros MOFs. En estos estudios hemos seguido principalmente tres aproximaciones: 1. La aproximación post-sintética de tipo Top-Down; 2. La aproximación de tipo Bottom-Up y 3. La modulación y el auto-ensamblaje de partículas. La publicación en el capítulo 3, vinculada a la aproximación post-sintética de tipo Top-Down, presenta la modificación controlada de las formas cristales de ZIF-8, para llegar a formas no alcanzables por procesos convencionales, a través de un ataque químico. Esta publicación trata de explicar el mecanismo que subyace en este “cincelado” anisotrópico de los cristales de ZIF-8. Para demostrar la posibilidad de generalizar este método con otros MOFs, también se presenta en esta publicación el “cincelado” anisotrópico de cristales de ZIF-67. La segunda publicación que corresponde al capítulo 4, está centrada en la aproximación post-sintética bottom-up, gracias a la cual el tamaño, la forma, la composición y la arquitectura del ZIF-8 y el ZIF-67 son modificadas con métodos de química húmeda. Esta publicación muestra la manipulación de los cristales de MOF a través del crecimiento paso a paso de otros MOFs, la funcionalización de partículas de MOFs con nanopartículas inorgánicas (InNPs) y finalmente, el diseño de un material compuesto MOF-InNP multicapa que puede ser usado como catalizador en reacciones de tipo cascada. La última publicación de esta tesis, en el capítulo 5, está en relación con la moducalción in-situ y el auto-ensamblaje de partículas de MOF. Esta publicación incluye la producción de partículas de MOF de tamaño y forma altamente monodispersa usando diferentes mudladores y surfactantes. En este sentido, partículas de ZIF-8 y UiO-66 altamente monodispersas con tamaños y formas diferentes se han producido usando el CTAB y el PVP, respectivamente, con índices de polidispersidad inferiores al 5 % para el ZIF-8 y el 8 % para el UiO-66. Esta publicación también incluye el autoensamblaje coloidal de estos cristales de MOF, a través del método de evaporación rápida, en superestructuras ordenadas en redes cristalinas bien definidas que se pueden usar como cristales fotónicos 3D. Finalmente, las propiedades fotónicas de estos cristales fotónicos de MOF y su uso como sensores de alcohol han sido estudiados.
The present Thesis aims to give the reader new insights on the controlled manipulation of Metal-Organic Framework (MOF) materials with nano-scale precision and its consequences in the final properties and applications. The study presented here hopes to form a bridge between MOFs and Nanotechnology; which means, bridging the classical expectations from the bulk properties of MOFs with novel functions that can arise upon the manipulation at the nano-scale. Here we demonstrate this bridging with a prototypical MOF, namely Zeolitic-Imidazolate Framework-8 (ZIF-8), which is one of the most studied MOF, due to its easy synthesis and promising properties including high porosity and exceeding thermal, chemical and water stability. The Thesis is organized into two parts. Chapter 1 constitutes the first part where the reader will find an introduction of the concept of porosity, with examples of naturally porous materials. This Chapter continues with a brief introduction of MOFs, an extensive introduction to ZIFs and, even more extensive introduction to ZIF-8. Thanks to the carefully selected examples and concepts, this introductory Chapter attempts to draw attention of the reader to the main point of this Thesis, which is the manipulation of MOFs at the nano-scale in order to reach beyond the classical aspects. The second part of this Thesis starts with a description of the objectives in Chapter 2. Then, each chapters 3, 4 and 5 includes a publication related to the manipulation of ZIF-8 at the nano-scale using ZIF-8 and -in some cases- other MOFs. In these studies, we followed three main approaches: 1. Post-synthetic top-down approach; 2. Post-synthetic bottom-up approach; and 3. In-situ modulation and self-assembly of particles. The publication in Chapter 3 is related to the post-synthetic top-down approach, explaining the anisotropic etching of ZIF-8 crystals to reach unprecedented shapes that are unachievable by conventional synthetic methods. The publication also attempts to explain the underlying mechanism of this anisotropic etching of ZIF-8 crystals. Also, to shed light on other MOFs and to prove the generality of the method, anisotropic etching of ZIF-67 crystals is demonstrated. The second publication, which constitutes Chapter 4, is centered on the post-synthetic bottom-up approach where the size, shape, composition and architecture of ZIF-8 and ZIF-67 crystals are modified using post-synthetic wet-chemistry. This publication explains the manipulation of MOF crystals by post-synthetic growing steps of other MOF layers, the functionalization of MOF particles with inorganic nanoparticles (InNPs) and finally, the design of complex multi-layered MOF-InNP composite materials that can be used as catalysts in cascade reactions. The last publication presented in this Thesis, in Chapter 5, is related to the in-situ modulation and self-assembly of MOF particles. This publication includes the production of MOF particles with very high size and shape monodispersity using surfactants as modulators. In this sense, highly monodisperse ZIF-8 and UiO-66 particles with various sizes and shapes were produced using CTAB and PVP, respectively, with polydispersive index < 5% for ZIF-8 and < 8% for UiO-66. It also includes the colloidal self-assembly of these MOF crystals via a fast droplet evaporation method to form ordered superstructures with well-defined crystalline superlattices that can be used as 3D photonic crystals when the particle size is selected appropriately. Finally, the photonic properties of these MOF photonic crystals and evaluation of this sensing capability of alcohol vapors are exploited.

A logical progression from the maturing field of colloidal semiconductor quantum dots to the emerging subclass of impurity-doped colloidal semiconductor nanoparticles is underway. To this end, the present work describes the formation and analysis of a new form of Tin-doped Indium Oxide (ITO). The form is that of a colloidal dispersion comprised of pure-phase, 4-6 nanometer ITO particles possessing an essentially single crystalline character. This system forms a non-agglomerated, optically clear solution in a variety of non-polar solvents and can remain in this state, at room temperature, for months and potentially, years. ITO is the most widely used member of the exotic materials family known as Transparent Conductive Oxides (TCOs) and is the primary enabling material behind a wide variety of opto-electronic device technologies. Material synthesis was achieved by initiating a series of interrelated nucleophilic substitution reactions that provided sufficient intensity to promote doping efficiencies greater than 90% for a wide range of tin concentrations. The optical clarity of this colloidal system allowed the intrinsic properties of single crystalline ITO particles to be evaluated prior to their use in thin-films or composite structures. Monitoring the temporal progression of n-type degeneracy by its effects on the optical properties of colloidal dispersions shed light on the fundamental issues of particle formation, band filling (Burstein-Moss) dynamics, and the very origin of n-type degeneracy in ITO. Central to these studies was the issue of excess electron character. The two limiting cases of entirely free and entirely confined electron motion were evaluated by application of bulk-like band dispersion analysis and the effective mass approximation, respectively. This provided a means to estimate the number of excess conduction band electrons present within an individual particle boundary. The ability to control and optimize the level of n-type degeneracy within the colloidal ITO nanoparticle form by compositional variation was also demonstrated. A key to the widespread adoption of a new material by industry is an ability to produce multi-gram and perhaps, kilogram quantities with no significant sacrifice in quality. Accordingly, a modified synthesis process was developed to allow for the mass production of high-quality colloidal ITO nanocrystals.

Dans cette thèse, de nouvelles stratégies pour la préparation de matériaux de type Metal-Organic-Frameworks (MOF) ont été étudiés et développés. L’électrodeposition bipolaire indirecte (IBED) a été utilisé pour préparer ZIF-8 et HKUST-1 sur des substrats métalliques de façon simple et avec une sélectivité spatiale. Ce concept devrait pouvoir être généralisée pour la synthèse de nombreux autres composés MOF, permettant ainsi une synthèse pas chère et verte, conduisant à de nouvelles générations de composites de type Janus basés sur des MOFs. En outre, des électrodes avec une structure hiérarchique macro-/ microporeux de HKUST-1 ont été préparées par une technique de dissolution-dépôt électrochimique. L'approche de synthèse mis au point est très pratique en ce qui concerne la durée des expériences, et ouvre diverses applications pour les MOFs. Enfin des nanoparticules de métaux nobles sur un substrat à base de MIL-101 ont été préparées comme la dernière partie de l'étude expérimentale par dépôt colloïdal. Ce concept peut être généralisé pour la synthèse d'autres composites nanoparticules métalliques / MOF, et pourrait améliorer l'activité catalytique des MOFs. En dehors de l'étude expérimentale, afin de comprendre mieux la catalyse de matériaux MOF, le comportement catalytique de Cu (II) dans le MOF-505 a été théoriquement étudié pour la réaction d'aldolisation Mukayiama par la théorie de densité fonctionnelle et comparé à celui d'un autre catalyseur, Cu-ZSM-5. En outre, le comportement catalytique d'amas homo- et hétéro-bimétalliques, qui sont des complexes métalliques qui représentent les agrégats métalliques dans les MOFs, a également été étudié théoriquement pour la réaction de cycloaddition de dioxyde de carbone et des oxydes d'éthylène
In this thesis, new strategies for the preparation of Metal 0rganic Frameworks (MOF) materials with designed structures were studied and developed. Indirect bipolar electrodeposition (IBED) was used to prepare ZIF-8 and HKUST-1 on metal substrates in a straightforward and site-selective way. This concept is expected to be able to be generalized for the synthesis of many other MOF compounds, thus allowing a cheap and green synthesis, leading to new generations of MOF-based Janus-type composites. Furthermore, rationally designed hierarchical macro-/microporous HKUST-1 electrodes were prepared via an electrochemical dissolution-deposition technique. The developed synthesis approach is very practical in terms of the time consumption, and opens up MOFs for various applications. Finally, MIL-101-supported noble metal nanoparticles were prepared as the last part of the experimental studies via a simple colloidal deposition technique. This concept might be generalized for the synthesis of other metal nanoparticle/MOF composites, and might improve the catalytic activity of MOFs. Apart from the experimental study, in order to gain a deeper insight into the catalysis of MOF materials, the catalytic behavior of Cu(II) in the paddle-wheel unit of MOF-505 was theoretically investigated for the Mukaiyama aldol reaction via the density functional theory and compared to that of another catalyst, Cu-ZSM-5 zeolite. Besides, the catalytic behavior of homo-metallic clusters and hetero-bimetallic clusters, that are the metal complexes representing the metal clusters in MOFs, were also theoretically investigated for the cycloaddition reaction of carbon dioxide and ethylene oxides