508 research outputs found

    Improving the gas sorption capacity in lantern-type metal-organic polyhedra by a scrambled cage method

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    The synthesis of multivariate metal-organic frameworks (MOFs) is a well-known method for increasing the complexity of porous frameworks. In these materials, the structural differences of the ligands used in the synthesis are sufficiently subtle that they can each occupy the same site in the framework. However, multivariate or ligand scrambling approaches are rarely used in the synthesis of porous metal-organic polyhedra (MOPs) – the molecular equivalent of MOFs – despite the potential to retain a unique intrinsic pore from the individual cage while varying the extrinsic porosity of the material. Herein we directly synthesise scrambled cages across two families of lantern-type MOPs and find contrasting effects on their gas sorption properties. In one family, the scrambling approach sees a gradual increase in the BET surface area with the maximum and minimum uptakes associated with the two pure homoleptic cages. In the other, the scrambled materials display improved surface areas with respect to both of the original, homoleptic cages. Through analysis of the gas sorption isotherms, we attribute this effect to the balance of micro- and mesoporosity within the materials, which varies as a result of the scrambling approach. The gas uptake of the materials presented here underscores the tunability of cages that springs from their combination of intrinsic, extrinsic, micro- and meso- porosities

    Grain boundaries in polycrystalline materials for energy applications : First principles modeling and electron microscopy

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    Polycrystalline materials are ubiquitous in technology, and grain boundaries have long been known to affect materials properties and performance. First principles materials modeling and electron microscopy methods are powerful and highly complementary for investigating the atomic scale structure and properties of grain boundaries. In this review, we provide an introduction to key concepts and approaches for investigating grain boundaries using these methods. We also provide a number of case studies providing examples of their application to understand the impact of grain boundaries for a range of energy materials. Most of the materials presented are of interest for photovoltaic and photoelectrochemical applications and so we include a more in depth discussion of how modeling and electron microscopy can be employed to understand the impact of grain boundaries on the behavior of photoexcited electrons and holes (including carrier transport and recombination). However, we also include discussion of materials relevant to rechargeable batteries as another important class of materials for energy applications. We conclude the review with a discussion of outstanding challenges in the field and the exciting prospects for progress in the coming years

    Crystal Structures of Metal Complexes

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    This reprint contains 11 papers published in a Special Issue of Molecules entitled "Crystal Structures of Metal Complexes". I will be very happy if readers will be interested in the crystal structures of metal complexes

    Local diffusion in the extracellular space of the brain

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    The brain extracellular space (ECS) is a vast interstitial reticulum of extreme morphological complexity, composed of narrow gaps separated by local expansions, enabling interconnected highways between neural cells. Constituting on average 20% of brain volume, the ECS is key for intercellular communication, and understanding its diffusional properties is of paramount importance for understanding the brain. Within the ECS, neuroactive substances travel predominantly by diffusion, spreading through the interstitial fluid and the extracellular matrix scaffold after being focally released. The nanoscale dimensions of the ECS render it unresolvable by conventional live tissue compatible imaging methods, and historically diffusion of tracers has been used to indirectly infer its structure. Novel nanoscopic imaging techniques now show that the ECS is a highly dynamic compartment, and that diffusivity in the ECS is more heterogeneous than anticipated, with great variability across brain regions and physiological states. Diffusion is defined primarily by the local ECS geometry, and secondarily by the viscosity of the interstitial fluid, including the obstructive and binding properties of the extracellular matrix. ECS volume fraction and tortuosity both strongly determine diffusivity, and each can be independently regulated e.g. through alterations in glial morphology and the extracellular matrix composition. Here we aim to provide an overview of our current understanding of the ECS and its diffusional properties. We highlight emerging technological advances to respectively interrogate and model diffusion through the ECS, and point out how these may contribute in resolving the remaining enigmas of the ECS.The authors acknowledge funding from the Spanish Ministry of Science and Innovation (PID2020-115896RJ-I00, PID2020-113894RB-I00, PCI2022-135040-2), the Basque Government (GIC21/76, GIU21/048), CIBERNED, Human Frontier Science Program (RGP0036/2020) and Aligning Science Across Parkinson's (ASAP-020505) through the Michael J. Fox Foundation for Parkinson's Research (MJFF)

    LIPIcs, Volume 261, ICALP 2023, Complete Volume

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    LIPIcs, Volume 261, ICALP 2023, Complete Volum

    Advanced 1,2,3-triazolate-based coordination compounds: from carbonic anhydrase mimics, molecular building blocks, and catalyst supports to electrically conducting spin-crossover MOFs

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    Kuratowski complexes and related metal-organic frameworks (MOF), especially of the MFU-4-type, built from 1,2,3-triazolate-based ligands gained increasing interest in the last years due to their variable side ligands and metal sites. Such materials and their post-synthetic modifications have shown an outstanding potential for applications such as adsorption, capture, separation and kinetic trapping of gases, drug delivery, atmospheric water harvesting, sensing, H2/D2 quantum sieving, investigation of fundamental magnetic phenomena, and in particular catalysis. In this respect, MFU-4-type MOF catalysts were shown to outperform other heterogeneous catalysts for the dimerization and polymerization of olefins with some applications already advancing toward commercial applicability. This thesis mainly aims to extend the functionality of 1,2,3-triazolate-based coordination materials via advanced linker designs, novel framework assembly strategies, and post-synthetic modifications, as well as through a better understanding of the underlying material properties. During this project, several new organic and complex building blocks, as well as advanced framework structures were prepared and characterized. Furthermore, additional emphasis was directed to the investigation and interpretation of resulting physical phenomena like phase transitions, magnetism, and electrical conductivity. The Zn-MFU-4l ([Zn5IICl4(BTDD)3]; H2-BTDD = bis(1H-1,2,3-triazolo[4,5-b][4′,5′-i])dibenzo[1,4]dioxin) and Co-MFU-4l ([Zn1.3IICo3.7IICl4(BTDD)3]) metal-organic frameworks were prepared according to the literature procedures and modified by a post-synthetic side ligand exchange of the chloride anions, which led to MFU-4-type structures featuring organometallic metal-carbon bonds. Overall, five new Zn-MFU-4l structures of the general formula [Zn5IILxCl4–x(BTDD)3] (4 ≥ x > 3; L = methanido, ethanido, n-butanido, tert-butanido, 3,3-dimethyl-1-butyn-1-ido; Zn-MFU-4l-Me, -Et, -n-Bu, -t-Bu, -Butyne) and two new Co-MFU-4l structures, Co-MFU-4l-Me ([Zn1.5IICo3.5IIMe3.1Cl0.9(BTDD)3]) and Co-MFU-4l-OH ([Zn1.4IICo3.6II (OH)3.1Cl0.9(BTDD)3]), were obtained. Such side ligands were not characterized for MFU-4-type MOFs before, although they are presumed responsible for the metal site activation during olefin catalysis reactions, which require organometallic co-catalysts. For this purpose, a combination of simulated and measured IR spectra was developed as well-suited characterization technique for such insoluble materials, which preclude analytical methods like liquid state NMR and mass spectroscopy. A high stability of the organometallic Zn-MFU-4l derivatives was observed, whereas the Co-MFU-4l-Me was of a pyrophoric nature and reacted upon water contact to Co-MFU-4l-OH, which exhibited a CO2 binding mechanism comparable to that of carbonic anhydrase. Synthesis of Kuratowski complexes built from 1H-benzotriazole-5,6-diamine (H-btda) ligands and post-synthetic exchange of the chloride side ligands with Tp/Tp* (Tp= hydrotris(pyrazolyl)borate; Tp* = hydrotris(3,5-dimethyl-1-pyrazolyl)borate) provided us with a variety of six-fold diamine-functionalized molecular building blocks intended for the development of novel MOF construction pathways. Crystallization of those compounds have already led to the assembly of porous metal hydrogen-bonded frameworks (M-HOF), some of which have even exhibited permanent porosity. This is a rare property of this material class, which is still in its infancy with only a few structures reported so far. Overall, five new metal hydrogen-bonded framework assemblies (CFA-20-X ((2,6-lutidinium)+[Zn5X4(btda)6X]−· n(DMF); X= Cl−, Br−), CFA-20-Tp, CFA-20-Tp*, CFA-20-Tp*-DMSO ([Zn5Y4(btda)6]; Y = Tp, Tp*) could be characterized, thus representing a significant contribution to this field of study. Although no MOFs could be crystallized from reactions of these complexes with metal salts, preliminary results have shown that direct incorporation of metal sites is a suitable pathway to convert M-HOFs into more stable MOFs. Taking the functionality of MFU-4-type frameworks to the next level, the novel 1,1',5,5'-tetrahydro-6,6'-biimidazo[4,5-f]benzotriazole (H4-bibt) ligand was developed to potentiate the post-synthetic modification possibilities compared to other MFU-4-type frameworks via introduction of additional and easily accessible biimidazole coordination sites at the linker backbone. This gave rise to the five most sophisticated MFU-4-type structures prepared so far. Post-synthetic Tp ligand exchange in the resulting MFU-4-type CFA-19 ([Co5IICl4(H2-bibt)3]) provided the stable CFA-19-Tp ([Co5IICl0.4Tp3.6(H2-bibt)3]) framework, in which the additional coordination sites were saturated in a third modification step with MIBr(CO)3 (M= Re, Mn) moieties or deprotonated via introduction of ZnEt moieties. The resulting materials exhibit high metal site density single-crystal X-ray structures with over 1700 atoms per unit cell for the ReBr(CO)3@CFA-19-Tp ([Co5IICl0.4Tp3.6(H2-bibt)3·(ReIBr(CO)3)2.8]) and a thermally induced release of all CO ligands for the MnBr(CO)3@CFA-19-Tp ([Co5IICl0.4Tp3.6(H2-bibt)3(MnIBr(CO)3)3]·3.1(MnIBr(CO)X)). Preliminary results also indicate a facile incorporation of other coordination moieties such as MIICl2 (M= PdII, PtII). These proof-of-principle incorporations of coordination moieties and open metal sites render such CFA-19-type scaffolds promising supports for an even larger variety of active species intended for the binding and activation of small molecules in future investigations. Coincidental synthesis of the novel CFA-23 ((((propan-2-yl)oxidanium)+[Mn6IICl5(ta)8]−; H-ta= 1H-1,2,3-triazole) coordination framework provided the opportunity to investigate changes of the resulting magnetic properties in comparison to a similar structure built from 1H-1,2,3-benzotriazole, as well as the ultra-narrow character of the pore channels in CFA-23. High purity samples of the literature-known Fe(ta)2 (H-ta= 1H-1,2,3-triazole) framework were prepared and investigated in detail to unveil its record hysteresis spin-crossover phase transition. Aiming at the use of Fe(ta)2 in surface acoustic wave-based sensor applications, experimental and theoretical insights into the material’s electrical conductivity changes upon adsorption of inert gases were assisted with the measurement of adsorption isotherms and the determination of the resulting isosteric enthalpies of adsorption

    Polímeros de coordinación porosos biocompatibles y su aplicación en catálisis y remediación ambiental

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    Esta tesis se enmarca en el campo de la Ciencia de Materiales y la Química de Coordinación, ya que se centra en el diseño de nuevos materiales porosos. Específicamente, explora la síntesis, caracterización y aplicaciones de nuevos Marcos Metal-Orgánicos (MOFs) basados en zinc. En general, los principales objetivos de esta tesis son dos. En primer lugar, obtener y caracterizar nuevos polímeros de coordinación porosos (MOFs) ensamblados con ligandos oxamidato derivados de biomoléculas como aminoácidos, así como metales biocompatibles como el zinc. En segundo lugar, estudiar las propiedades y aplicaciones potenciales de estos materiales. En este sentido, se pretende proporcionar ejemplos de aplicaciones prácticas que muestren el potencial de estos nuevos MOFs, enfatizando así la importancia de estos compuestos en diferentes áreas tecnológicas. Los resultados obtenidos tienen como objetivo contribuir a la expansión del conocimiento dentro de mi grupo de investigación en relación a la síntesis de nuevos MOFs. Para lograr estos objetivos, se han llevado a cabo las siguientes tareas: (i) Diseñar procedimientos sintéticos adecuados para obtener MOFs a gran escala (polvo microcristalino) y monocristales, lo que permite su caracterización mediante difracción de rayos X de monocristal. Para este propósito, se han utilizado métodos de precipitación directa y métodos de difusión lenta, respectivamente. (ii) Estudiar las características físicas y químicas de los nuevos materiales obtenidos para poder aplicarlos en campos donde puedan mostrar un mejor rendimiento. Para ello, se han empleado varias técnicas de caracterización comúnmente utilizadas para este tipo de compuestos. Estas técnicas incluyen difracción de rayos X de monocristal (SCXRD), difracción de rayos X de polvo (PXRD), análisis elemental (EA), espectroscopía infrarroja (FT-IR), análisis termogravimétrico (TGA) y adsorción de N2. (iii) Explorar las posibles propiedades físicas y químicas de los materiales recién sintetizados y las aplicaciones que puedan surgir a partir de ellos. Cabe destacar que algunos de estos estudios se han llevado a cabo en colaboración con otros grupos de investigación. En particular, las mediciones catalíticas se han realizado en colaboración con el profesor Antonio Leyva (UPV-CSIC), y la resolución estructural se ha llevado a cabo en colaboración con la profesora Donatella Armentano de la Universidad de Calabria (Italia). Los resultados obtenidos en este trabajo se clasifican en tres capítulos diferentes. En el capítulo 2, se presenta un nuevo MOF a base de zinc (ZnII2-serimox) que es amigable con el medio ambiente, estable en agua y derivado del aminoácido natural L-serina. Este MOF fue capaz de degradar eficientemente soluciones acuosas del colorante verde brillante en tan solo 120 minutos mediante fotocatálisis. La degradación total se siguió mediante espectroscopía UV-Vis y se confirmó mediante cristalografía de rayos X de monocristal, revelando la presencia de CO2 dentro de sus canales. Estudios de reutilización demuestran la robustez estructural y de rendimiento de ZnII2-serimox. En el capítulo 3, se presenta un nuevo MOF a base de zinc derivado del aminoácido S-metil-L-cisteína (CaIIZnII6-Mecysmox), que posee canales funcionales capaces de acomodar e interactuar con antibióticos y catalizar la hidrólisis selectiva de los antibióticos penicilínicos amoxicilina y ceftriaxona. En particular, el MOF CaIIZnII6-Mecysmox degrada eficientemente el anillo β-lactámico de cuatro miembros de la amoxicilina, actuando como un mimético de la β-lactamasa y ampliando el número muy limitado de MOFs capaces de imitar procesos enzimáticos catalíticos. Estudios combinados de difracción de rayos X de monocristal y cálculos funcionales de densidad (DFT) ofrecen información única sobre las interacciones entre los huéspedes y las moléculas de amoxicilina en los canales funcionales de CaIIZnII6-Mecysmox. Esto permite proponer un mecanismo de degradación basado en la activación de una molécula de agua promovida por un grupo hidroxilo puente de zinc, que ataca de forma nucleofílica el grupo carbonilo y rompe el enlace C-N del anillo lactámico. En el capítulo 4, se presenta otro MOF a base de zinc, isoreticular al mostrado en el capítulo 3, pero con una pequeña diferencia en su composición: la sustitución de los cationes de Ca(II) por cationes de Sr(II), lo que ha resultado en una mayor robustez del material. Aprovechando las propiedades catalíticas de los átomos de Zn(II) y los espacios confinados que esta estructura ofrece, incluyendo el tamaño poroso y los sitios metálicos abiertos disponibles, este MOF fue capaz de catalizar la cicloadición del óxido de etileno y el óxido de propileno con CO2 para obtener carbonatos de etileno y propileno, con rendimientos de hasta el 95% y selectividad completa. Estos resultados confirman aún más el poder catalítico que los MOFs tienen en la síntesis selectiva de productos industrialmente relevantes, proporcionando una alternativa atractiva a los catalizadores heterogéneos actuales.This thesis falls within the field of Materials Science and Coordination Chemistry, as it focuses on the design of new porous materials. Specifically, it explores the synthesis, characterization, and applications of new Zn-based Metal-Organic Frameworks (MOFs). In general, the main objectives of this thesis are twofold. Firstly, to obtain and characterize new porous coordination polymers (MOFs) assembled with oxamidate ligands derived from biomolecules such as amino acids, as well as biocompatible metals like zinc. Secondly, to study the properties and potential applications of these materials. In this sense, I aim to provide real-life examples showcasing the potential applications of these new MOFs, thereby emphasizing the significance of these compounds in different technological areas. The obtained results are intended to contribute to the expansion of knowledge within my research group regarding the synthesis of novel MOFs. To achieve these objectives, the following tasks have been carried out: (i) Designing suitable synthetic procedures to obtain MOFs on a large scale (microcrystalline powder) and single crystals, thereby enabling their characterization through single-crystal X-ray diffraction. For this purpose, direct precipitation methods and slow diffusion methods have been employed, respectively. (ii) To study the physical and chemical characteristics of the newly obtained materials in order to apply them in fields where they can demonstrate better performance, several commonly used characterization techniques for these types of compounds have been employed. These techniques include single-crystal X-ray diffraction (SCXRD), powder X-ray diffraction (PXRD), elemental analysis (EA), infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA) and N2 adsorption. (iii) Explore the potential physical and chemical properties of the newly synthesized materials and the applications that may arise from them. It is worth noting that some of these studies have been conducted in collaboration with other research groups. In particular, catalytic measurements have been carried out in collaboration with Professor Antonio Leyva (UPV-CSIC), and structural resolution has been conducted in collaboration with Professor Donatella Armentano from the University of Calabria (Italy). The results obtained in this work are classified intro three different chapters. In chapter 2, it is present a novel bio-friendly water-stable Zn-based MOF (ZnII2-serimox), derived from the natural amino acid L-serine, which was able to efficiently photodegrade water solutions of brilliant green dye in only 120 min. The total degradation was followed by UV-Vis spectroscopy and further confirmed by single-crystal X-ray crystallography, revealing the presence of CO2 within its channels. Reusability studies further demonstrate the structural and performance robustness of ZnII2-serimox. In chapter 3, a novel Zn-based metal–organic framework derived from the amino acid S-methyl-L-cysteine is presented (CaIIZnII6-Mecysmox), possessing functional channels capable to accommodate and interact with antibiotics, which catalyze the selective hydrolysis of the penicillinic antibiotics amoxicillin and ceftriaxone. In particular, MOF CaIIZnII6-Mecysmox degrades, very efficiently, the four-membered β-lactam ring of amoxicillin, acting as a β-lactamase mimic, expanding the very limited number of MOFs capable of mimicking catalytic enzymatic processes. Combined single crystal X-ray diffraction (SCXRD) studies and density functional (DFT) calculations offer unique snapshots on the host guest-interactions established between amoxicillin and the functional channels of CaIIZnII6-Mecysmox. This allows to propose a degradation mechanism based on the activation of a water molecule, promoted by a Zn-bridging hydroxyl group, concertedly to the nucleophilic attack to the carbonyl moiety and the cleaving of C-N bond of the lactam ring. In chapter 4, another Zn-based metal-organic framework isoreticular to the previous one shown in chapter 3 is presented (SrIIZnII6-Mecysmox) with a slight different in composition- the substitution of Ca(II) cations with Sr(II) ones- which has resulted in enhanced robustness of the material. Taking advantage of the catalytic properties of Zn(II) atoms and the confined spaces that this structure offer, porous size and available open metal sites, this MOF was able to catalyze the cycloaddition of ethylene oxide and propylene oxide with CO2 to obtain ethylene and propylene carbonates, obtaining yields up to 95% and complete selectivity. These results further confirm the catalytic power that MOFs have in selective syntheses of industrially relevant products, providing an appealing alternative to the current heterogeneous catalysts
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