Los autores agradecen a la Agencia de Reducción de Amenazas de Defensa para financiar con el número de proyectos BA07PRO104, Martin Smith, Corrine Stone, y Colin Willis de la Ciencia y Tecnología de Laboratorio de Defensa (DSTL) por su experiencia en la tecnología de plasma de baja presión, y Matthew Browe y Wesley Gordon de la química Center Edgewood Biológica (ECBC) para pruebas y mediciones microbreakthrough ángulo de contacto, respectivamente.

1. Cu-BTC Síntesis y Preparación <ol><li> Revuelva 12,5 ml de agua desionizada y 12,5 ml de dimetilformamida en 100 ml de tornillo frasco con tapa durante aproximadamente 5 min. </li><li> Añadir 0,87 g (3,6 mmol) de cobre (II) trihidrato de nitrato seguido de 0,50 g (2,4 mmoles) de ácido trimésico a la solución en el frasco y se agita durante aproximadamente 5 min. La solución se volverá de color azul. Coloque el frasco tapado en el horno precalentado a 120 ° C durante aproximadamente 24 horas. </li><li> Retire el frasco de la estufa. Una vez que el frasco se ha enfriado a temperatura ambiente, recuperar los cristales de Cu-BTC a través de filtración a vacío utilizando papel de filtro nominal para recuperar cristales mayores o iguales a 2,5 micras. Enjuague los cristales resultantes con diclorometano, en última instancia, la colocación de los cristales en una solución fresca de diclorometano. </li><li> Cambie el disolvente cada 24 horas y reemplazar con diclorometano fresco para los próximos tres días para ayudar en la eliminación de los disolventes menos volátiles de los poros de Cu-BTC. </li><li> Calentar los cristales de Cu-BTC a 170 ° C en un horno de vacío o por medio de una línea de Schlenk de quitar cualquier moléculas huésped residuales del material. Totalmente activado Cu-BTC debe ser azul a morado oscuro en color. </li><li> Confirme la estructura y la composición química de Cu-BTC mediante difracción de rayos X y de Fourier espectroscopia infrarroja con transformada, respectivamente. </li></ol> 2. Plasma Enhanced Chemical Vapor Deposition de perfluoroalcanos en Cu-BTC 14 <ol><li> Antes de cada experimento limpiar el reactor de plasma y cualquier material de vidrio para ser utilizado en el tratamiento de plasma con un plasma de aire a 50 W durante al menos 30 min. Esto elimina cualquier películas perfluoroalcano que puedan haberse formado en las superficies interiores de la cámara de reacción o el material de vidrio a partir de experimentos anteriores. </li><li> Coloque una cantidad conocida de activado Cu-BTC en una botella ml Pyrex 250 y se extendió a lo largo de la botella en su lado para asegurar un tratamiento homogéneo. Una tela permeable debe ser colocado alrededor de lacuello de la botella con una banda de goma para reducir al mínimo la cantidad de muestra que se pierde al aplicar un vacío. </li><li> Colocar el frasco en la cámara de plasma. Aplicar un vacío hasta que la cámara alcanza una presión de ≤ 0,20 mbar durante al menos 30 minutos para eliminar el agua que pueda haber adsorbido en la muestra. </li><li> Conectar el gas perfluoroalcano y ajustar el regulador a una presión dentro de las especificaciones del controlador de flujo de masa. </li><li> Ajuste el controlador de flujo másico para llenar la cámara de reacción con la cantidad apropiada de gas perfluoroalcano para mantener la presión deseada del experimento. Girar la botella dentro del aparato de PECVD para crear un tratamiento más homogénea del polvo. </li><li> Encender el plasma con un generador de 13,56 MHz de RF, y sintonizar la frecuencia de radio con la unidad de acoplamiento LC para maximizar la potencia y reducir al mínimo la reflectancia. Vuelva a sintonizar periódicamente durante todo el tratamiento. </li><li> Una vez finalizado el tratamiento, evacuar la cámara de cualquierde gas perfluoroalcano residual y luego ventilación a la presión atmosférica. Retirar la muestra del aparato de PECVD y recuperar el material tratado desde los lados de la botella. Un dispositivo antiestático se debe utilizar para recuperar la máxima cantidad de material. </li><li> Coloque el material tratado en un horno a 120 ° C para eliminar cualquier gas perfluoroalcano sin reaccionar. Después se coloca el material tratado en un desecador para evitar la adsorción de agua de la atmósfera. </li><li> Enjuague el material residual que queda en la botella y el filtro para recuperar los residuos para su eliminación adecuada. </li><li> Caracterizar el tratado Cu-BTC con 20 F de ángulo mágico de giro de resonancia magnética nuclear, transformada de Fourier espectroscopía infrarroja y espectroscopía de fotoelectrones de rayos x. </li></ol> 3. El envejecimiento de Cu-BTC bajo Húmedo Condiciones <ol><li> Ajuste la temperatura deseada y la humedad relativa de la cámara ambiental y deje que se equilibre. </li><li> Distribuya la muestra uniformemente enun recipiente abierto y colocar en la cámara ambiental para la cantidad de tiempo deseada. </li><li> Caracterizar la muestra de Cu-BTC con difracción de rayos X y una isoterma de nitrógeno a 77 K para determinar el grado de degradación. </li></ol> 4. Experimentos Microbreakthrough Amoníaco 2 <ol><li> Preparar un lastre 14,6 L de amoníaco a 5.000 mg / m 3 por primera inyección de un lastre vacío con 210 ml de amoniaco aseado. A continuación, llenar el lastre con aire cero a una presión de 15 psi. Conecte el lastre de conformidad con el aparato microbreakthrough. </li><li> Ejecutar un tubo en blanco en el aparato de microbreakthrough para determinar la señal de alimentación. Establecer controladores de flujo másico para amoníaco y aire seco a 8 y 12 ml / min, respectivamente, para crear un flujo de 20 ml / min de 2000 mg / m 3 amoniaco. Ejecutar un método programado para controlar el cromatógrafo de gases y detector de fotoionización para determinar la señal de alimentación de amoniaco en el efluente. La humedad puede ser añadido al sistemasi se desea mediante la ejecución de parte de la corriente de diluyente a través de una célula saturador de temperatura controlada a una velocidad necesaria para alcanzar la humedad relativa requerida. </li><li> Colocar una pequeña cantidad de lana de vidrio por debajo de la frita de vidrio en un tubo de vidrio nominal de 4 mm de diámetro. Pesar aproximadamente 10-15 mg de material en el tubo. La masa utilizada debe dar lugar a aproximadamente 55 mm 3 de volumen de sorbente, lo que resulta en un tiempo de residencia lecho de aproximadamente 0,15 seg. </li><li> Flujo de aire seco a través del tubo de vidrio, ya que se calienta a 150 ° C durante 1 hora para eliminar el agua adsorbida. Pesar la muestra después de la regeneración. </li><li> Colocar la muestra en línea y asegurar en posición vertical en un baño de agua a 25 ° C. </li><li> Establecer los controladores de flujo másico para amoníaco y aire seco a 8 y 12 ml / min, respectivamente, para crear un flujo de 20 ml / min a 2.000 mg / m 3 amoniaco mientras que se evita la muestra a las líneas de llenado con el gas de alimentación. </li><li> El flujo de la corriente de amoniaco a través de la muestra y ejecutar un programadométodo para controlar el cromatógrafo de gases y detector de fotoionización para monitorear la concentración de amoniaco en el efluente. </li><li> Una vez que la concentración del efluente ha alcanzado la concentración de alimentación, desconecte la corriente de amoníaco y permitir que la muestra fuera de gas amoníaco que no se absorbe fuertemente a la muestra. </li><li> Retire la muestra del baño de agua para el análisis posterior a la exposición a través de la difracción de rayos X y transformación de Fourier análisis infrarrojo. </li><li> Integrar la señal del cromatógrafo de gas frente a los datos de tiempo para determinar la carga de amoníaco para la muestra. </li></ol>

<ol>
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Los autores declaran que no tienen intereses financieros en competencia.

La síntesis de Cu-BTC, como en la mayoría de MOF, puede depender en gran medida de la relación de los reactivos utilizados y la temperatura de la síntesis se lleva a cabo a. La variación de la temperatura o disolvente utilizado en la síntesis se ha demostrado que producen diferentes morfologías de una estructura de MOF 20. Por lo tanto es de gran importancia para seguir el procedimiento establecido en la literatura para cualquier MOF está sintetizando. Además, se debe considerar los reactivos, disolv...

Armazones organometálicos (MOF) se han convertido en un líder en su clase de materiales porosos para la eliminación de gases tóxicos 1-3. MOF tienen una capacidad sin precedentes para adaptar la funcionalidad de interacción química específica. Cu-BTC (también conocido como HKUST-1 o Cu 3 (BTC) 2) se ha encontrado previamente para tener una carga excepcionalmente alta de amoníaco, sin embargo, esto es a un costo de la estabilidad 4 estructural del material. Otros estudios sobre Cu-BTC han indicado que la humedad en sí es capaz de degradar la estructura de MOF, haciéndolo ineficaz para muchas aplicaciones potenciales 5,6,21. La inestabilidad estructural de cierto carboxilato que contiene MOF en la presencia de agua líquida o alta humedad ha sido un obstáculo importante para utilizar en aplicaciones comerciales o industriales 7. Sería más ideal para MOF utilizados para la eliminación química de tener estabilidad inherente en la presencia de humedad. Sin embargo, muchos MOFs con una estabilidad superior, como UiO-66, tienen capacidades deficientes de eliminación de productos químicos, mientras que muchos MOF con sitios de metal abiertas como MOF-74 y Cu-BTC tienen capacidad para la eliminación química superiores 2,4,8,9. Los sitios de metal abierto en MOF-74 y Cu-BTC mejorar la absorción de los gases tóxicos tales como amoníaco, pero estos sitios también son susceptibles a la retención de agua, el envenenamiento de los sitios activos y en muchos casos conduce a la descomposición estructural. Con el fin de preservar las propiedades químicas de un agua inestable MOF, se han hecho diversos intentos para mejorar la estabilidad en el agua de MOF. MOF-5 se ha demostrado que tiene una mejora en resistencia a la humedad tras el tratamiento térmico, mediante la creación de una capa carbonosa alrededor del MOF, sin embargo, el aumento de la hidrofobicidad es a expensas de la superficie y en última instancia funcionalidad proveerá 10. MOF-5 también se ha demostrado que tiene su hidroestabilidad aumentó a través de dopaje con Ni 2 + iones 11. Además, 1,4-diazabiciclo [2.2.2] octano contieneMOF ING (también conocidos como DMOFs) se han utilizado para mostrar la afinación de la estabilidad de agua a través de la incorporación de diversos grupos colgantes sobre el enlazador dicarboxilato de 1,4-benceno 12,13. La falta de hidroestabilidad de algunos de MOF, las específicamente con elevada captación de gas tóxico, llevó al uso de plasma de mayor deposición de vapor químico (PECVD) de perfluoroalcanos para crear grupos fluorados en las superficies de la MOF para aumentar su hidrofobicidad 14. Esta técnica ofrece la ventaja única que se puede utilizar para alterar cualquier MOF que contiene hidrógenos aromáticos, así como otros grupos funcionales potenciales sobre las superficies interiores de MOF. Sin embargo, la técnica puede ser difícil de controlar debido a la formación de radicales altamente reactivos en el plasma. Los radicales no sólo reaccionan con los átomos de hidrógeno aromáticos, sino también con CF x grupos que ya reaccionaron sobre las superficies de MOF. Es necesario un control cuidadoso del procedimiento para garantizar blo porockage no ocurre, lo que hace ineficaz la MOF. Esta técnica ha sido utilizada por otros para alterar las propiedades de humectación de los materiales de carbono, sin embargo, a nuestro conocimiento nunca había sido previamente utilizado para mejorar hidroestabilidad de material microporoso 15,16..

<table border="1">
	<tbody>
		<tr>
			<td>Name of Material/ Equipment</td>
			<td>Company</td>
			<td>Catalog Number</td>
			<td>Comments/Description</td>
		</tr>
		<tr>
			<td>Copper (II) Nitrate Trihydrate</td>
			<td>Sigma-Aldrich</td>
			<td>61194</td>
			<td></td>
		</tr>
		<tr>
			<td>Trimesic acid</td>
			<td>Sigma-Aldrich</td>
			<td>482749</td>
			<td></td>
		</tr>
		<tr>
			<td>Ethanol</td>
			<td>Sigma-Aldrich</td>
			<td>130147</td>
			<td></td>
		</tr>
		<tr>
			<td>Dimethyl Formamide</td>
			<td>Sigma-Aldrich</td>
			<td>319937</td>
			<td></td>
		</tr>
		<tr>
			<td>Dichloromethane</td>
			<td>Sigma-Aldrich</td>
			<td>187332</td>
			<td></td>
		</tr>
		<tr>
			<td>Hexafluoroethane</td>
			<td>Synquest Labs</td>
			<td>1100-2-05</td>
			<td></td>
		</tr>
		<tr>
			<td>Femto-Plasma System</td>
			<td>Diener Electronic</td>
			<td>Basic unit type B</td>
			<td></td>
		</tr>
		<tr>
			<td>Plasma Generator</td>
			<td>Diener Electronic</td>
			<td>Type D</td>
			<td>0-100 W at 13.56 MHz</td>
		</tr>
		<tr>
			<td>Rotary Vane Pump for Plasma System</td>
			<td>Leybold</td>
			<td>D16BCS PFPE</td>
			<td>Appropriate for corrosive gases</td>
		</tr>
		<tr>
			<td>Powder Treatment Device</td>
			<td>Diener Electronic</td>
			<td>Option 5.9</td>
			<td>Glass bottle and rotating devise within plasma system</td>
		</tr>
		<tr>
			<td>Environmental Chamber</td>
			<td>Associated Environmental Systems</td>
			<td>HD-205</td>
			<td></td>
		</tr>
		<tr>
			<td>Gas Chromatograph</td>
			<td>Hewlet Packard</td>
			<td>HP5890 Series II</td>
			<td></td>
		</tr>
		<tr>
			<td>Photoionization Detector</td>
			<td>O-I Analytical</td>
			<td>4430/5890</td>
			<td></td>
		</tr>
		<tr>
			<td>Photoionization Detector Lamp</td>
			<td>Excilitis</td>
			<td>FK-794U</td>
			<td></td>
		</tr>
		<tr>
			<td>Water bath</td>
			<td>NESLAB</td>
			<td>RTE-111</td>
			<td></td>
		</tr>
		<tr>
			<td>Fritted glass tubes</td>
			<td>CDA Analytical</td>
			<td>MX062101</td>
			<td>Dynatherm sampling tubes</td>
		</tr>
	</tbody>
</table>

preparation of hydrophobic metal-organic frameworks via plasma enhanced chemical vapor deposition of perfluoroalkanes for the removal of ammonia

Plasma mayor deposición de vapor químico (PECVD) de perfluoroalcanos mucho tiempo se ha estudiado para el ajuste de las propiedades de humectación de las superficies. Para materiales microporosos de alta área de superficie, tales como armazones organometálicos (MOF), desafíos únicos se presentan para los tratamientos PECVD. Aquí se presenta el protocolo para el desarrollo de un MOF que antes era inestable a condiciones de humedad. El protocolo describe la síntesis de Cu-BTC (también conocido como HKUST-1), el tratamiento de Cu-BTC con PECVD de perfluoroalcanos, el envejecimiento de los materiales en condiciones de humedad, y los posteriores experimentos microbreakthrough amoníaco en cantidades de miligramos de materiales microporosos. Cu-BTC tiene un área superficial muy alta (~ 1800 m 2 / g) en comparación con la mayoría de los materiales o superficies que han sido previamente tratados por métodos PECVD. Parámetros tales como presión de la cámara y el tiempo de tratamiento son muy importantes para garantizar el plasma penetra a perfluoroalcano y reaccionars con las superficies interiores de MOF. Además, el protocolo para los experimentos microbreakthrough amoníaco establecidos aquí se puede utilizar para una variedad de gases de prueba y materiales microporosos.

<html> Dentro de los resultados representativos los autores eligieron para mostrar las características de una muestra de 0,50 g de Cu-BTC tratados con hexafluoroetano (C 2 6 F) durante 4 horas a una presión de 0,30 mbar y una potencia de plasma de 50 W. MOF tratados con un plasma perfluoroalcano en condiciones adecuadas debería mostrar una mayor hidrofobicidad. Esto se puede comprobar colocando el polvo en la parte superior del agua líquida y la determinación de si los flotadores de la muestra o medir el ...

Watch this Scientific Journal Video about Preparation of Hydrophobic Metal-Organic Frameworks via Plasma Enhanced Chemical Vapor Deposition of Perfluoroalkanes for the Removal of Ammonia at JoVE.com

Preparation of Hydrophobic Metal-Organic Frameworks via Plasma Enhanced Chemical Vapor Deposition of Perfluoroalkanes for the Removal of Ammonia

Aquí se describen los procedimientos de plasma mayor deposición de vapor químico de perfluoroalcanos sobre materiales microporosos tales como armazones organometálicos para mejorar su estabilidad y la hidrofobicidad. Además, las pruebas de penetración de cantidades de miligramos de muestras se describe en detalle.

Preparación de hidrófobos orgánicos marcos de metal a través de Plasma Enhanced Chemical Vapor Deposition de perfluoroalcanos para la eliminación de amoniaco

Plasma enhanced chemical vapor deposition (PECVD) of perfluoroalkanes has long been studied for tuning the wetting properties of surfaces. For high ...

preparation-hydrophobic-metal-organic-frameworks-via-plasma-enhanced

Research

JoVE Journal

Chemistry

15.4K vistas.  Science Applications International Corporation (SAIC).  Aquí se describen los procedimientos de plasma mayor deposición de vapor químico de perfluoroalcanos sobre materiales microporosos tales como armazones organometálicos para mejorar su estabilidad y la hidrofobicidad. Además, las pruebas de penetración de cantidades de miligramos de muestras se describe en detalle. 

Video: Preparation of Hydrophobic Metal-Organic Frameworks via Plasma Enhanced Chemical Vapor Deposition of Perfluoroalkanes for the Removal of Ammonia

Synthesis and Characterization of Functionalized Metal-organic Frameworks

Metal-organic frameworks have attracted extraordinary amounts of research attention, as they are attractive candidates for numerous industrial and technological applications. Their signature property is their ultrahigh porosity, which however imparts a series of challenges when it comes to both constructing them and working with them. Securing desired MOF chemical and physical functionality by linker/node assembly into a highly porous framework of choice can pose difficulties, as less porous and more thermodynamically stable congeners (e.g., other crystalline polymorphs, catenated analogues) are often preferentially obtained by conventional synthesis methods. Once the desired product is obtained, its characterization often requires specialized techniques that address complications potentially arising from, for example, guest-molecule loss or preferential orientation of microcrystallites. Finally, accessing the large voids inside the MOFs for use in applications that involve gases can be problematic, as frameworks may be subject to collapse during removal of solvent molecules (remnants of solvothermal synthesis). In this paper, we describe synthesis and characterization methods routinely utilized in our lab either to solve or circumvent these issues. The methods include solvent-assisted linker exchange, powder X-ray diffraction in capillaries, and materials activation (cavity evacuation) by supercritical CO2 drying. Finally, we provide a protocol for determining a suitable pressure region for applying the Brunauer-Emmett-Teller analysis to nitrogen isotherms, so as to estimate surface area of MOFs with good accuracy.

Synthesis, activation, and characterization of intentionally designed metal-organic framework materials is challenging, especially when building blocks are incompatible or unwanted polymorphs are thermodynamically favored over desired forms. We describe how applications of solvent-assisted linker exchange, powder X-ray diffraction in capillaries and activation via supercritical CO2 drying, can address some of these challenges.

Marcos de síntesis y caracterización de funcionalizado metal-orgánico

Metal-organic frameworks have attracted extraordinary amounts of research attention, as they are attractive candidates for numerous industrial and ...

Investigación

Química

Chemical Vapor Deposition of an Organic Magnet, Vanadium Tetracyanoethylene

Recent progress in the field of organic materials has yielded devices such as organic light emitting diodes (OLEDs) which have advantages not found in traditional materials, including low cost and mechanical flexibility. In a similar vein, it would be advantageous to expand the use of organics into high frequency electronics and spin-based electronics. This work presents a synthetic process for the growth of thin films of the room temperature organic ferrimagnet, vanadium tetracyanoethylene (V[TCNE]x, x~2) by low temperature chemical vapor deposition (CVD). The thin film is grown at &#60;60 &#176;C, and can accommodate a wide variety of substrates including, but not limited to, silicon, glass, Teflon and flexible substrates. The conformal deposition is conducive to pre-patterned and three-dimensional structures as well. Additionally this technique can yield films with thicknesses ranging from 30 nm to several microns. Recent progress in optimization of film growth creates a film whose qualities, such as higher Curie temperature (600 K), improved magnetic homogeneity, and narrow ferromagnetic resonance line-width (1.5 G) show promise for a variety of applications in spintronics and microwave electronics.

We present the synthesis of the organic-based ferrimagnet vanadium tetracyanoethylene (V[TCNE]x, x~2) via low temperature chemical vapor deposition (CVD). This optimized recipe yields an increase in Curie temperature from 400 K to over 600 K and a dramatic improvement in magnetic resonance properties.

Deposición de vapor químico de un imán Orgánica, vanadio tetracianoetileno

Recent progress in the field of organic materials has yielded devices such as organic light emitting diodes (OLEDs) which have advantages not found in ...

Epitaxial Growth of Perovskite Strontium Titanate on Germanium via Atomic Layer Deposition

Atomic layer deposition (ALD) is a commercially utilized deposition method for electronic materials. ALD growth of thin films offers thickness control and conformality by taking advantage of self-limiting reactions between vapor-phase precursors and the growing film. Perovskite oxides present potential for next-generation electronic materials, but to-date have mostly been deposited by physical methods. This work outlines a method for depositing SrTiO3 (STO) on germanium using ALD. Germanium has higher carrier mobilities than silicon and therefore offers an alternative semiconductor material with faster device operation. This method takes advantage of the instability of germanium's native oxide by using thermal deoxidation to clean and reconstruct the Ge (001) surface to the 2&#215;1 structure. 2-nm thick, amorphous STO is then deposited by ALD. The STO film is annealed under ultra-high vacuum and crystallizes on the reconstructed Ge surface. Reflection high-energy electron diffraction (RHEED) is used during this annealing step to monitor the STO crystallization. The thin, crystalline layer of STO acts as a template for subsequent growth of STO that is crystalline as-grown, as confirmed by RHEED. In situ X-ray photoelectron spectroscopy is used to verify film stoichiometry before and after the annealing step, as well as after subsequent STO growth. This procedure provides framework for additional perovskite oxides to be deposited on semiconductors via chemical methods in addition to the integration of more sophisticated heterostructures already achievable by physical methods.

This work details the procedures for the growth and characterization of crystalline SrTiO3 directly on germanium substrates by atomic layer deposition. The procedure illustrates the ability of an all-chemical growth method to integrate oxides monolithically onto semiconductors for metal-oxide semiconductor devices.

Crecimiento epitaxial de perovskita del titanato de estroncio en el germanio a través de deposición de capas atómicas

Atomic layer deposition (ALD) is a commercially utilized deposition method for electronic materials. ALD growth of thin films offers thickness control and ...

Aerosol-assisted Chemical Vapor Deposition of Metal Oxide Structures: Zinc Oxide Rods

Whilst columnar zinc oxide (ZnO) structures in the form of rods or wires have been synthesized previously by different liquid- or vapor-phase routes, their high cost production and/or incompatibility with microfabrication technologies, due to the use of pre-deposited catalyst-seeds and/or high processing temperatures exceeding 900 &#176;C, represent a drawback for a widespread use of these methods. Here, however, we report the synthesis of ZnO rods via a non-catalyzed vapor-solid mechanism enabled by using an aerosol-assisted chemical vapor deposition (CVD) method at 400 &#176;C with zinc chloride (ZnCl2) as the precursor and ethanol as the carrier solvent. This method provides both single-step formation of ZnO rods and the possibility of their direct integration with various substrate types, including silicon, silicon-based micromachined platforms, quartz, or high heat resistant polymers. This potentially facilitates the use of this method at a large-scale, due to its compatibility with state-of-the-art microfabrication processes for device manufacture. This report also describes the properties of these structures (e.g., morphology, crystalline phase, optical band gap, chemical composition, electrical resistance) and validates its gas sensing functionality towards carbon monoxide.

Columnar zinc oxide structures in the form of rods are synthesized via aerosol-assisted chemical vapor deposition without the use of pre-deposited catalyst-seed particles. This method is scalable and compatible with various substrates based on either silicon, quartz or polymers.

Aerosol-asistida por deposición de Vapor químico del óxido de Metal estructuras: barras de óxido de Zinc

Whilst columnar zinc oxide (ZnO) structures in the form of rods or wires have been synthesized previously by different liquid- or vapor-phase routes, ...

Surface Functionalization of Metal-Organic Frameworks for Improved Moisture Resistance

Metal-organic frameworks (MOFs) are a class of porous inorganic materials with promising properties in gas storage and separation, catalysis and sensing. However, the main issue limiting their applicability is their poor stability in humid conditions. The common methods to overcome this problem involve the formation of strong metal-linker bonds by using highly charged metals, which is limited to a number of structures, the introduction of alkylic groups to the framework by post-synthetic modification (PSM) or chemical vapour deposition (CVD) to enhance overall hydrophobicity of the framework. These last two usually provoke a drastic reduction of the porosity of the material. These strategies do not permit to exploit the properties of the MOF already available and it is imperative to find new methods to enhance the stability of MOFs in water while keeping their properties intact. Herein, we report a novel method to enhance the water stability of MOF crystals featuring Cu2(O2C)4&#160;paddle-wheel units, such as HKUST (where HKUST stands for Hong Kong University of Science &#38; Technology), with the catechols functionalized with alkyl and fluoro-alkyl chains. By taking advantage of the unsaturated metal sites and the catalytic catecholase-like activity of CuII ions, we are able to create robust hydrophobic coatings through the oxidation and subsequent polymerization of the catechol units on the surface of the crystals under anaerobic and water-free conditions without disrupting the underlying structure of the framework. This approach not only affords the material with improved water stability but also provides control over the function of the protective coating, which enables the development of functional coatings for the adsorption and separations of volatile organic compounds. We are confident that this approach could also be extended to other unstable MOFs featuring open metal sites.

Robust functional catechol coatings were produced in one step by direct reaction of the material known as HKUST with synthetic catechols under anaerobic conditions. The formation of homogeneous coatings surrounding the entire crystal is ascribed to the biomimetic catalytic activity of Cu(II) dimers on the external surface of the crystals.

Funcionalización de superficies de Metal-Organic Frameworks para resistencia a la humedad mejorada

Metal-organic frameworks (MOFs) are a class of porous inorganic materials with promising properties in gas storage and separation, catalysis and sensing. ...

Development of Heterogeneous Enantioselective Catalysts using Chiral Metal-Organic Frameworks (MOFs)

Substrate size discrimination by the pore size and homogeneity of the chiral environment at the reaction sites are important issues in the validation of the reaction site in metal-organic framework (MOF)&#8211;based catalysts in an enantioselective catalytic reaction system. Therefore, a method of validating the reaction site of MOF-based catalysts is necessary to investigate this issue. Substrate size discrimination by pore size was accomplished by comparing the substrate size versus the reaction rate in two different types of carbonyl-ene reactions with two kinds of MOFs. The MOF catalysts were used to compare the performance of the two reaction types (Zn-mediated stoichiometric and Ti-catalyzed carbonyl-ene reactions) in two different media. Using the proposed method, it was observed that the entire MOF crystal participated in the reaction, and the interior of the crystal pore played an important role in exerting chiral control when the reaction was stoichiometric. Homogeneity of the chiral environment of MOF catalysts was established by the size control method for a particle used in the Zn-mediated stoichiometric reaction system. The protocol proposed for the catalytic reaction revealed that the reaction mainly occurred on the catalyst surface regardless of the substrate size, which reveals the actual reaction sites in MOF-based heterogeneous catalysts. This method for reaction site validation of MOF catalysts suggests various considerations for developing heterogeneous enantioselective MOF catalysts.

Development of Heterogeneous Enantioselective Catalysts using Chiral Metal-Organic Frameworks MOFs

Here, we present a protocol for active site validation of metal-organic framework catalysts by comparing stoichiometric and catalytic carbonyl-ene reactions to find out whether a reaction takes place on the inner or outer surface of metal-organic frameworks.

Desarrollo de catalizadores enantioselectivos heterogéneos utilizando marcos metálicos-orgánicos quirales (MOF)

Substrate size discrimination by the pore size and homogeneity of the chiral environment at the reaction sites are important issues in the validation of ...

Synthesis of Single-Crystalline Core-Shell Metal-Organic Frameworks

Because of their designability and unprecedented synergistic effects, core-shell metal-organic frameworks (MOFs) have been actively examined recently. However, the synthesis of single-crystalline core-shell MOFs is very challenging, and thus a limited number of examples have been reported. Here, we suggest a method of synthesizing single-crystalline HKUST-1@MOF-5 core-shells, which is HKUST-1 at the center of MOF-5. Through the computational algorithm, this pair of MOFs was predicted to have the matched lattice parameters and chemical connection points at the interface. To construct the core-shell structure, we prepared the octahedral- and cubic-shaped HKUST-1 crystals as a core MOF, in which the (111) and (001) facets were mainly exposed, respectively. Via the sequential reaction, the MOF-5 shell was well-grown on the exposed surface, showing a seamless connect interface, which resulted in the successful synthesis of single-crystalline HKUST-1@MOF-5. Their pure phase formation was proved by optical microscopic images and powder X-ray diffraction (PXRD) patterns. This method presents the potential of and insights into the single-crystalline core-shell synthesis with different kinds of MOFs.

Here, we demonstrate a protocol for the two-step synthesis of single-crystalline core-shells using a non-isostructural metal-organic framework (MOF) pair, HKUST-1 and MOF-5, which have well-matched crystal lattices.

Síntesis de estructuras metal-orgánicas de núcleo monocristalino

Because of their designability and unprecedented synergistic effects, core-shell metal-organic frameworks (MOFs) have been actively examined recently. ...

A Technical Guide for Performing Spectroscopic Measurements on Metal-Organic Frameworks

Metal-organic frameworks (MOFs) offer a unique platform to understand light-driven processes in solid-state materials, given their high structural tunability. However, the progression of MOF-based photochemistry has been hindered by the difficulty in spectrally characterizing these materials. Given that MOFs are typically larger than 100 nm in size, they are prone to excessive light scatter, thereby rendering data from valuable analytical tools like transient absorption and emission spectroscopy nearly uninterpretable. To gain meaningful insights of MOF-based photo-chemical and physical processes, special consideration must be taken toward properly preparing MOFs for spectroscopic measurements, as well as the experimental setups that garner higher quality data. With these considerations in mind, the present guide provides a general approach and set of guidelines for the spectroscopic investigation of MOFs. The guide addresses the following key topics: (1) sample preparation methods, (2) spectroscopic techniques/measurements with MOFs, (3) experimental setups, (3) control experiments, and (4) post-run stability characterization. With appropriate sample preparation and experimental approaches, pioneering advancements toward the fundamental understanding of light-MOF interactions are significantly more attainable.

Here, we use a polymer stabilizer to prepare metal-organic framework (MOF) suspensions that exhibit markedly decreased scatter in their ground-state and transient absorption spectra. With these MOF suspensions, the protocol provides various guidelines to characterize the MOFs spectroscopically to yield interpretable data.

Una guía técnica para realizar mediciones espectroscópicas en estructuras metal-orgánicas

Metal-organic frameworks (MOFs) offer a unique platform to understand light-driven processes in solid-state materials, given their high structural ...

Síntesis de MOF de baja valencia a partir de enlazadores de fosfina multitópicos

Experimental Approaches for the Synthesis of Low-Valent Metal-Organic Frameworks from Multitopic Phosphine Linkers

Metal-organic frameworks (MOFs) are the subject of intense research focus due to their potential applications in gas storage and separation, biomedicine, energy, and catalysis. Recently, low-valent MOFs (LVMOFs) have been explored for their potential use as heterogeneous catalysts, and multitopic phosphine linkers have been shown to be a useful building block for the formation of LVMOFs. However, the synthesis of LVMOFs using phosphine linkers requires conditions that are distinct from those in the majority of the MOF synthetic literature, including the exclusion of air and water and the use of unconventional modulators and solvents, making it somewhat more challenging to access these materials. This work serves as a general tutorial for the synthesis of LVMOFs with phosphine linkers, including information on the following: 1) the judicious choice of the metal precursor, modulator, and solvent; 2) the experimental procedures, air-free techniques, and required equipment; 3) the proper storage and handling of the resultant LVMOFs; and 4) useful characterization methods for these materials. The intention of this report is to lower the barrier to this new subfield of MOF research and facilitate advancements toward novel catalytic materials.

Autor destacado: Enfoques experimentales para la síntesis de marcos metal-orgánicos de baja valente a partir de enlazadores de fosfina multitópicos  

Here, we describe a protocol for the synthesis of low-valent metal-organic frameworks (LVMOFs) from low-valent metals and multitopic phosphine linkers under air-free conditions. The resulting materials have potential applications as heterogeneous catalyst mimics of low-valent metal-based homogeneous catalysts.

Enfoques experimentales para la síntesis de estructuras metal-orgánicas de baja valencia a partir de enlaces de fosfina multitópicos

Metal-organic frameworks (MOFs) are the subject of intense research focus due to their potential applications in gas storage and separation, biomedicine, ...