Os autores agradecem a Agência de Defesa Redução de Ameaças para financiamento sob o número projeto BA07PRO104, Martin Smith, Corrine Stone, e Colin Willis do Laboratório de Ciência e Tecnologia de Defesa (DSTL) por sua expertise em tecnologia de baixa pressão plasma e Mateus Browe e Wesley Gordon de Centro Edgewood Chemical Biológica (ECBC) para testes e medições microbreakthrough ângulo de contato, respectivamente.

1. Cu-BTC Síntese e Preparação <ol><li> Agita-se 12,5 ml de água desionizada e 12,5 ml de dimetilformamida em 100 ml de tampa de rosca frasco durante aproximadamente 5 min. </li><li> Adicionar 0,87 g (3,6 mmol) de cobre (II) tri-hidrato de nitrato seguido por 0,50 g (2,4 mmol) de ácido trimésico para a solução no frasco e agita-se durante cerca de 5 min. A solução fica azul na cor. Colocar o frasco tapado num forno pré-aquecido a 120 ° C durante aproximadamente 24 horas. </li><li> Retire o frasco do forno. Uma vez que o frasco foi arrefecido até à temperatura ambiente, recuperar os cristais de Cu-BTC através de filtração sob vácuo, utilizando papel de filtro nominal para recuperar cristais maiores do que ou iguais a 2,5 mM. Lavar os cristais resultantes com diclorometano, em última análise, colocando os cristais em uma solução de diclorometano fresco. </li><li> Trocar o solvente a cada 24 horas e substitui-se com diclorometano fresco para os três dias seguintes para ajudar na remoção de solventes voláteis a menos de os poros de Cu-BTC. </li><li> Aquecer os cristais Cu-BTC a 170 ° C num forno de vácuo, ou através de uma linha de Schlenk a remover quaisquer moléculas hóspedes residuais a partir do material. Totalmente ativado Cu-BTC deve ser profundo azul para na cor roxa. </li><li> Confirme a estrutura e composição química de Cu-BTC via pó difração de raios-x e com transformada de Fourier espectroscopia no infravermelho, respectivamente. </li></ol> 2. Plasma aprimorado Chemical Vapor Deposition de perfluoroalcanos sobre Cu-BTC 14 <ol><li> Antes de cada experiência limpar o reactor de plasma e qualquer material de vidro para ser usado no tratamento de plasma com um plasma de ar de 50 W durante pelo menos 30 min. Isso remove todos os filmes perfluoroalkane que se possam ter formado sobre as superfícies internas da câmara de reacção ou do material de vidro a partir de experiências anteriores. </li><li> Coloque uma quantidade conhecida de ativado Cu-BTC em um pirex ml garrafa 250 e se espalhou por toda a garrafa de lado para garantir um tratamento homogêneo. Um pano permeável deve ser colocada em torno dogargalo da garrafa, com uma faixa de borracha para minimizar a quantidade de amostra que se perde após a aplicação de um vácuo. </li><li> Coloque a garrafa na câmara de plasma. Aplicar um vácuo até que a câmara de pressão atingiu um ≤ 0,20 mbar, durante pelo menos 30 minutos para remover qualquer água que possa ter adsorvido na amostra. </li><li> Ligue o gás perfluoroalkane e ajustar o regulador de pressão dentro das especificações do controlador de fluxo de massa. </li><li> Ajustar o controlador de fluxo de massa para encher a câmara de reacção com a quantidade adequada de gás perfluoroalkane para manter a pressão desejada do experimento. Rodar a garrafa dentro do dispositivo de DVQIP de criar um tratamento mais homogéneo do pó. </li><li> Acenda o plasma com um gerador de 13,56 MHz RF e sintonizar a freqüência de rádio com a unidade correspondente LC para maximizar o poder, minimizando a reflectância. Sintonizar periodicamente ao longo do tratamento. </li><li> Uma vez que o tratamento está completo, evacuar a câmara de qualquergás perfluoroalkane residual e depois vazão a pressão atmosférica. Retirar a amostra do dispositivo de DVQIP e recuperar o material tratado a partir dos lados da garrafa. Um dispositivo anti-estática deve ser utilizado para recuperar a quantidade máxima de material. </li><li> Colocar o material tratado num forno a 120 ° C para remover qualquer gás que não reagiu perfluoroalkane. Seguidamente, colocar o material tratado num exsicador para evitar a adsorção de água a partir da atmosfera. </li><li> Lavar o material residual na garrafa e filtrar para recuperar os resíduos para o descarte adequado. </li><li> Caracterizar o tratado Cu-BTC com 20 F ângulo mágico girando ressonância magnética nuclear, com transformada de Fourier espectroscopia no infravermelho e espectroscopia de fotoelétrons de raios-x. </li></ol> 3. Envelhecimento da Cu-BTC sob condições úmidas <ol><li> Regule a temperatura desejada e umidade relativa da câmara ambiental e permitir que ele se equilibre. </li><li> Espalhar a amostra uniformemente emum recipiente aberto e lugar na câmara ambiental para o período de tempo desejado. </li><li> Caracterizar a amostra de Cu-BTC com difracção de raios-x e um isotérmica de azoto a 77 K para determinar o grau de degradação. </li></ol> 4. Experimentos Amônia Microbreakthrough 2 <ol><li> Prepare um lastro de 14,6 L de amônia a 5.000 mg / m 3, primeiro injetar um lastro vazio com 210 ml de amônia pura. Em seguida, encher o balastro com ar de zero a uma pressão de 15 psi. Ligue o balastro de acordo com o aparelho microbreakthrough. </li><li> Executar um tubo vazio no aparelho microbreakthrough para determinar o sinal de alimentação. Definir os controladores de fluxo de massa para amoníaco e ar seco para 8 e 12 ml / min, respectivamente, para criar um fluxo de 20 ml / min de 2,000 mg / m 3 de amoníaco. Executar um método programado para controlar o cromatógrafo de gás e detector de fotoionização para determinar o sinal de alimentação de amoníaco no efluente. A humidade pode ser adicionado ao sistemase desejado, executando uma parte do fluxo de diluente através de uma célula de saturação, com temperatura controlada, a uma taxa necessária para alcançar a humidade relativa necessária. </li><li> Colocar uma pequena quantidade de lã de vidro abaixo da frita de vidro em um 4 mm de diâmetro nominal do tubo de vidro. Pesar cerca de 10-15 mg de material para dentro do tubo. A massa usada deve resultar em cerca de 55 mm 3 de volume de adsorvente, o que resulta num tempo de residência de cama de aproximadamente 0,15 segundos. </li><li> Fluxo de ar seco através do tubo de vidro quando é aquecido a 150 ° C durante 1 hora para remover qualquer água adsorvida. Pesa-se a amostra, após a regeneração. </li><li> Coloque a amostra na linha e garantir vertical em um banho-maria regulado a 25 ° C. </li><li> Definir os controladores de fluxo de massa de amoníaco e ar seco para 8 e 12 ml / min, respectivamente, para criar um fluxo de 20 ml / min a 2000 mg / m 3 de amoníaco, ignorando a amostra para as linhas de enchimento, com o gás de alimentação. </li><li> Vazão do fluxo de amônia através da amostra e executar um programadoMétodo para controlar o cromatógrafo de gás e detector de fotoionização para monitorizar a concentração de amoníaco no efluente. </li><li> Uma vez que a concentração do efluente atingiu a concentração de alimentação, desligar a corrente de amoníaco e deixar a amostra para fora do gás de amoníaco que não é fortemente adsorvido para a amostra. </li><li> Retirar a amostra do banho de água para análise pós-exposição via difração de raios-x e análise de Fourier-transform infravermelho. </li><li> Integrar o sinal cromatógrafo de gás vs os dados de tempo para determinar a carga de amoníaco para a amostra. </li></ol>

<ol>
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Os autores declaram que não têm interesses financeiros concorrentes.

A síntese de Cu-BTC, como na maioria dos MOF, pode ser fortemente dependente da proporção dos reagentes utilizados e da temperatura a síntese realiza-se a. Variando a temperatura ou solvente utilizado na síntese foi mostrado para produzir diferentes morfologias de uma estrutura MOF 20. Portanto, é de grande importância para seguir o processo descrito na literatura por qualquer MOF ser sintetizado. Além disso, deve-se considerar os reagentes, solventes e condições de síntese na escolha de um navio e...

Estruturas metálicas-orgânica (SDMO) estão se tornar um líder de classe de materiais porosos para a remoção de gases tóxicos 1-3. MOFs tem uma capacidade sem precedentes para adaptar a funcionalidade de interação química alvo. Cu-BTC (também conhecido como HKUST-1 ou Cu 3 (BTC), 2) tenha sido previamente encontrado para ter um nível excepcionalmente elevado de carga de amoníaco, no entanto, isto é, com um custo de estabilidade estrutural do material de 4. Outros estudos sobre Cu-BTC indicam que a própria humidade é capaz de degradar a estrutura MOF, tornando-o ineficaz para muitas aplicações potenciais 5,6,21. A instabilidade estrutural de certos carboxilato contendo MOF, na presença de água líquida ou de alta humidade tem sido um importante impedimento à utilização em aplicações comerciais ou industriais 7. Seria ideal para MOF utilizados para a remoção de produtos químicos para ter estabilidade inerente na presença de humidade. No entanto, muitos MOFs com estabilidade superior, como UiO-66, têm capacidades de remoção química pobres, enquanto muitos MOFs com sites de metal abertos como MOF-74 e Cu-BTC tem capacidades de remoção química superiores 2,4,8,9. Os locais de metal aberto em MOF-74 e Cu-BTC aumentar a absorção de gases tóxicos, como amônia, mas esses sites também são suscetíveis a ligação de água, envenenando os sítios ativos e, em muitos casos, levando ao colapso estrutural. De modo a preservar as propriedades químicas de uma água instável MOF, várias tentativas para melhorar a estabilidade da água de MOF foram feitas. MOF-5 demonstrou ter um aumento na resistência à humidade por tratamento térmico, através da criação de uma camada carbonácea em torno do MOF, no entanto, o aumento da hidrofobicidade é à custa da área de superfície e, finalmente, a funcionalidade 10. MOF-5 também tem sido demonstrado que a sua hydrostability aumentada através de dopagem com Ni 2 + iões 11. Além disso, o 1,4-diazabiciclo [2.2.2] octano contêmMOF ing (também conhecidos como DMOFs) têm sido usados ​​para mostrar a afinação de estabilidade de água através da incorporação de vários grupos pendentes no dicarboxilato ligante 1,4-benzeno 12,13. A falta de hydrostability de certos MOF, especificamente aquelas com elevada absorção de gás tóxico, levou à utilização de deposição de vapor químico de plasma melhorado (PECVD) de perfluoroalcanos para criar grupos fluorados sobre as superfícies do MOF para aumentar a sua hidrofobicidade 14. Esta técnica oferece a vantagem única que pode ser usada para alterar qualquer MOF contendo hidrogénios aromáticos, bem como outros grupos funcionais potenciais sobre as superfícies internas de MOF. No entanto, a técnica pode ser difícil de controlar, devido à formação de radicais altamente reactivos no plasma. Os radicais não só reagem com os átomos de hidrogénio aromáticos, mas também com FC x grupos já reagiram sobre as superfícies MOF. O controle cuidadoso do procedimento é necessário para garantir blo porosckage não ocorre, tornando o MOF ineficaz. Esta técnica tem sido utilizada por outras pessoas para alterar as propriedades umectantes de materiais de carbono, no entanto, para o nosso conhecimento, nunca haviam sido usados ​​para melhorar hydrostability 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

Deposição de vapor químico enriquecidos com plasma (PECVD) de perfluoroalcanos tem sido estudado para ajustar as propriedades umectantes de superfícies. Para a área de superfície elevada materiais microporosos, como estruturas metal-orgânicas (MOFs), desafios se apresentam para tratamentos PECVD. Nisto o protocolo para o desenvolvimento de um MOF que foi anteriormente instáveis ​​a condições de humidade são apresentados. O protocolo descreve a síntese de Cu-BTC (também conhecido como HKUST-1), o tratamento de Cu-BTC com PECVD de perfluoroalcanos, o envelhecimento dos materiais em condições úmidas, e os experimentos amônia microbreakthrough subseqüentes em quantidades de miligramas de materiais microporosos. Cu-BTC tem uma área extremamente elevada superfície (~ 1.800 m 2 / g) quando comparado com a maioria dos materiais ou superfícies que tenham sido previamente tratados por métodos PECVD. Parâmetros como pressão da câmara eo tempo de tratamento são de extrema importância para garantir a plasma perfluoroalkane penetra e reagirs com as superfícies internas do MOF. Além disso, o protocolo para experiências microbreakthrough amoníaco definidos aqui podem ser utilizados para uma variedade de gases de ensaio e materiais microporosos.

<html> Dentro dos resultados representativos, os autores escolheram a exibir as características de uma amostra de 0,50 g de Cu-BTC tratada com hexafluoroetano (C 2 F 6), durante 4 horas, a uma pressão de 0,30 mbar e uma potência de 50 W. plasma MOF tratados com um plasma perfluoroalkane em condições adequadas deve exibir reforçada hidrofobia. Isto pode ser demonstrado através da colocação do pó no topo de água em estado líquido e a determinação se os flutuadores de amostra ou a mediç?...

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

Aqui os processos de deposição de vapor químico de plasma aumentada de perfluoroalcanos sobre materiais microporosos tais como os quadros metal-orgânicos para melhorar a sua estabilidade e hidrofobicidade são descritos. Além disso, o teste de ruptura de quantidades de miligrama de amostras está descrita em detalhe.

Preparação de hidrofóbicos Metal-Organic Frameworks via Plasma aprimorado Chemical Vapor Deposition de perfluoroalcanos para a remoção de amônia

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

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Chemistry

15.4K visualizações.  Science Applications International Corporation (SAIC).  Aqui os processos de deposição de vapor químico de plasma aumentada de perfluoroalcanos sobre materiais microporosos tais como os quadros metal-orgânicos para melhorar a sua estabilidade e hidrofobicidade são descritos. Além disso, o teste de ruptura de quantidades de miligrama de amostras está descrita em detalhe. 

Vídeo: 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.

Síntese e caracterização de funcionalizados metal-organic frameworks

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

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.

Chemical Vapor Deposition de um ímã Orgânica, vanádio 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.

Crescimento epitaxial de Perovskita titanato de estrôncio em Germânio via deposição de camadas Atomic

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.

Aerossol-assistida de deposição de Vapor químico de estruturas de óxido de Metal: hastes de óxido de zinco

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.

Functionalization superfície de estruturas Metal-orgânicas para resistência à umidade melhorada

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.

Desenvolvimento de catalisadores enantioseseseseses heterogêneos usando estruturas quirais metal-orgânicas (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 ...

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.

Síntese de estruturas metal-orgânicas de núcleo cristalino único

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.

Um Guia Técnico para a Realização de Medições Espectroscópicas em Estruturas Metal-Orgânicas

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

Síntese de MOFs de baixa valência a partir de ligantes 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 em destaque: Abordagens experimentais para a síntese de estruturas metal-orgânicas de baixa valência a partir de ligantes 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.

Abordagens Experimentais para a Síntese de Estruturas Metal-Orgânicas de Baixa Valência a partir de Ligantes Multitópicos de Fosfina

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