Name: Solvothermal Synthesis and Isolation of the Crystalline Material Al-CAU-60
Uploaded: 2023-10-06T14:20:00
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solvothermal synthesis and isolation of the crystalline material al-cau-60

Síntese e descoberta de MOFs à base de fosfonatos: uma abordagem solvotérmica

Metal-organic frameworks (MOFs) are porous, crystalline compounds whose structures consist of metal-containing nodes, like metal ions or metal-oxygen clusters, which are connected by organic molecules (linkers)1. By varying the metal-containing nodes as well as the linker, a variety of compounds can be obtained that exhibit a wide range of properties and therefore have potential applications in different fields1.
The stability of a material is important for its application1,2,3. Therefore, MOFs containing tri- or tetravalent metal ions, such as Al3+, Cr3+, Ti4+, or Zr4+, with carboxylate2 or phosphonate4 linker molecules have been the focus of many investigations5,6,7. In addition to the direct synthesis of stable MOFs, the enhancement of stability through post-synthetic modifications as well as the formation of composites is a field of interest2. Phosphonate-based MOFs have been less often reported compared to carboxylate-based MOFs8. One reason is the higher coordination flexibility of the CPO32- group compared to the -CO2- group, which often leads to the formation of dense structures and greater structural diversity8,9,10,11. In addition, phosphonic acids often must be synthesized, as they are rarely available on the market. While some metal phosphonates exhibit exceptional chemical stability10, systematic access to isoreticular metal phosphonate MOFs, which allows the tuning of properties, is still a topic of high relevance12,13. Different strategies for the synthesis of porous metal phosphonates have been investigated, such as incorporating defects into otherwise dense layers, for example, by partially replacing phosphonate with phosphate ligands4,14. However, as defective structures are poorly reproducible, and the pores are not uniform, other strategies have been developed. In recent years, the use of sterically demanding or orthogonalized phosphonic acids as linker molecules have emerged as a suitable strategy for the preparation of porous metal phosphonates4,8,10,11,13,15,16,17,18. However, a universal synthesis route for porous metal phosphonates has not yet been discovered. As a result, the synthesis of metal phosphonates is often a process of trial and error, requiring the investigation of many synthesis parameters.
The parameter space of a reaction system includes chemical and process parameters and can be vast19. It consists of parameters such as the type of starting material (metal salt), molar ratios of starting materials, additives for pH adjustment, modulators, type of solvent, solvent mixtures, volumes, reaction temperatures, times, etc.19,20. A moderate number of parameter variations can easily result in several hundred individual reactions, making a carefully considered synthesis plan and well-chosen parameter space necessary. For example, a simple study using six molar ratios of the linker to the metal (e.g., M:L = 1:1, 1:2, ... to 1:6) and four different concentrations of an additive and keeping the other parameter constant, leads already to 6 x 4 = 24 experiments. Using four concentrations, five solvents, and three reaction temperatures would necessitate carrying out the 24 experiments 60 times, resulting in 1,440 individual reactions.
High-throughput (HT) methods are based on the concepts of miniaturization, parallelization, and automation, to varying degrees depending on the scientific question being addressed19,20. As such, they can be used to accelerate the investigation of multi-parameter systems and are an ideal tool for the discovery of new compounds, as well as synthesis optimization19,20. HT methods have been used successfully in different fields, ranging from drug discovery to materials science20. They have also been used for the investigation of porous materials such as zeolites and MOFs in solvothermal reactions, as recently summarized20. A typical HT workflow for solvothermal synthesis consists of six steps (Figure 1)19,20,21: a) selection of the parameter space of interest (i.e., the design of experiment [DOE]), which can be done manually or by using software; b) dosing of the reagents into the vessels; c) solvothermal synthesis; d) isolation and workup; e) characterization, which is typically done with powder X-ray diffraction (PXRD); and f) data evaluation, which is followed by step one again.
Parallelization and miniaturization are achieved in solvothermal reactions through the use of multiclaves, often based on the well-established 96-well plate format most commonly used in biochemistry and pharmacy19,20,22,23. Various reactor designs have been reported and several groups have constructed their own reactors19,20. Reactor choice depends on the chemical system of interest, especially the reaction temperature, (autogenous) pressure, and reactor stability19,20. For example, in a systematic study of zeolitic imidazolate frameworks (ZIFs), Banerjee et al.25 used the 96-well glass plate format to perform over 9600 reactions24. For reactions under solvothermal conditions, customized polytetrafluoroethylene (PTFE) blocks, or multiclaves with 24 or 48 individual PTFE inserts, have been described among others by the Stock group19,20.&#160;They are routinely employed, for example, in the synthesis of metal carboxylates and phosphonates. As such, Reinsch et al.25 reported the advantages of the methodology in the field of porous aluminum MOFs25. The in-house made HT reactor systems (Figure 2), which allow 24 or 48 reactions to be studied simultaneously, contain PTFE inserts with a total volume of 2.655 mL and 0.404 mL, respectively (Figure 2A,B). Usually, no more than 1 mL or 0.1 mL, respectively, is used. While these reactors are used in conventional ovens, microwave-assisted heating using SiC blocks and small glass vessels has also been reported26.
The automation of studies leads to time savings and improved reproducibility, as influence of the human factor is minimized20. The degree to which automation has been used varies strongly19,20. Fully automated commercial systems, including pipetting20 or weighting capabilities20, are known. A recent example is the use of a liquid-handling robot to study ZrMOFs, reported by the group of Rosseinsky27. Automated analysis can be performed by PXRD using a diffractometer equipped with an xy stage. In another example, a plate reader was used to screen solid-state catalysts, mainly MOFs, for HT screening of nerve agent degradation28. Samples can be characterized in a single run without the need for manual sample or position changes. Automation does not eliminate human error, but it reduces the possibility of its occurring19,20.
Ideally, all steps in a HT workflow should be adapted in terms of parallelization, miniaturization, and automation to eliminate possible bottlenecks and maximize efficiency. However, if it is not possible to establish a HT workflow in its entirety, it may be helpful to adopt selected steps/tools for one&#39;s own research. The use of multiclaves for 24 reactions is particularly useful here. The technical drawings of the in-house made equipment used in this study (as well as others) are published for the first time and can be found in Supplementary File 1, Supplementary File 2, Supplementary File 3, and Supplementary File 4.

Autor em destaque: Acelerando a descoberta na química de materiais microporosos 

Descoberta e Otimização da Síntese de Compostos Metal-Orgânicos Isoreticulares à Base de Al(III) Fosfonato Usando Métodos de Alto Rendimento

I see the periodic table as a huge playground, and in our research, we focus on the synthesis of new materials, porous materials, such as this here. That's a structural model, and we see holes in the framework. and that can be used to store molecules or also to separate molecules based on the size of these.And in addition to that kind of studies, we also develop new reactor systems in order to accelerate the discovery process. The current experimental challenges are to further accelerate the synthesis and characterization process with additional high throughput instrumentation, such as high throughput absorption characterization device. The lack of detail in publications regarding the synthesis and characterization procedure affecting reproducibility is a well-known problem in chemistry.By providing a thorough description of our method and setup, we aim to encourage other groups to adopt the described methodology, thereby increasing the reproducibility of experimental studies. We do not know what the future will bring since we work on the discovery of new materials, and we never know what kind of properties these materials will have. Nevertheless, I think that the use of linker molecules from renewable feedstocks will play a major role.And regarding the application, the use in sensing and the separation of gas molecules will be very important.

Watch this Scientific Journal Video about Solvothermal Synthesis and Isolation of the Crystalline Material Al-CAU-60 at JoVE.com

Solvothermal Synthesis and Isolation of the Crystalline Material Al-CAU-60  

Síntese Solvotérmica e Isolamento do Material Cristalino Al-CAU-60

Para começar, adicione o ligante H4PMP como sólido às pastilhas de politetrafluoretileno, ou PTFE, para Al-CAU-60. Em seguida, use uma pipeta para adicionar a solução de cloreto de alumínio, água desmineralizada e a solução de aditivos às pastilhas. Insira os discos na placa de amostra e coloque as pastilhas de PTFE preenchidas na placa de amostra.Marque a placa de aterramento do reator de forma a permitir a identificação das pastilhas de PTFE e insira a placa de amostra com as pastilhas de PTFE preenchidas na placa de aterramento. Prepare duas folhas de PTFE e coloque-as nas placas de amostra garantindo cobertura total. Certifique-se de que a folha de PTFE está corretamente posicionada e se encaixa na placa principal usando os pinos de guia.Adicione os parafusos e aperte-os com a mão. Em seguida, sele o reator inicialmente fechado com a ajuda de uma prensa mecânica ou hidráulica e aperte os parafusos manualmente novamente. Coloque a multiclave em um forno de convecção forçada programável.Para Al-CAU-60, defina o programa de tempo de temperatura mostrado na tela. Em seguida, inicie o programa de tempo de temperatura. Retire o multiclave do forno.Depois de esfriar até a temperatura ambiente, coloque-o em uma prensa mecânica ou hidráulica e comprima suavemente até que os parafusos possam ser soltos manualmente. Coloque a multiclave dentro de uma coifa e remova a placa principal do reator. Em seguida, remova as folhas de PTFE e a placa de amostra com as pastilhas de PTFE da placa de aterramento do reator.Agora monte o bloco de filtragem de alto rendimento conectando o bloco de filtro a uma bomba de vácuo por meio de duas garrafas de lavagem. Coloque dois papéis de filtro entre duas esteiras de vedação de silicone com as reentrâncias correspondentes no bloco do filtro. Em seguida, coloque o bloco de enchimento de PTFE por cima, garantindo que as reentrâncias apropriadas correspondam aos tapetes de teto e ao bloco de filtro.Aperte as camadas usando a estrutura de fixação, que é mantida no lugar por seis parafusos de pino. Para selar corretamente a unidade, use porcas de asa nos parafusos de pino e aperte-os à mão. Feche os recessos do bloco de enchimento que não devem ser preenchidos com plugues.Ligue a bomba de vácuo de membrana e configure-a para um modo no qual ela bombeará para o melhor vácuo possível. Transfira o conteúdo das pastilhas de PTFE para os poços designados do bloco de enchimento com pipetas descartáveis. Quando todas as pastilhas estiverem vazias, dê uma segunda olhada nos cristais e isole-os, se presentes.Desmonte cuidadosamente o bloco de filtração assim que todos os poços forem drenados. Uma biblioteca de produtos agora está disponível em papel filtro. Deixe secar ao ar livre dentro do exaustor.Coloque a biblioteca de produtos entre a placa de base e a placa de cobertura para caracterizar o produto obtido por difração de raios X de pó posteriormente. Certifique-se de que os recessos e as placas correspondam aos locais do produto. Após o alinhamento das placas, fixe-as com dois parafusos.Insira a biblioteca de produtos no suporte de amostra do difratômetro. Coloque cuidadosamente o porta-amostras carregado no estágio XY do difratômetro. Feche o instrumento antes de iniciar as medições.O espaço de parâmetros é mostrado nesta figura. As sínteses com hidróxido de sódio como aditivo são destacadas em azul, as sínteses sem aditivo são destacadas em verde, e as sínteses com o aditivo ácido clorídrico são destacadas em laranja e vermelho. As razões molares dos reagentes são mostradas no lado esquerdo e na parte superior.O gráfico empilhado de todos os padrões de difração de raios X de pó medidos é mostrado nesta figura. Aqui, o aditivo hidróxido de sódio é destacado em azul, nenhum aditivo é destacado em verde e o aditivo ácido clorídrico é destacado em vermelho. Os nomes das amostras são mostrados aqui que se correlacionam com as razões molares das matérias-primas utilizadas na mistura de síntese.Estes resultados sugerem que os produtos com baixa cristalinidade foram obtidos a partir da síntese onde a razão molar hidróxido de sódio para alumínio foi de um para um, ou nenhum hidróxido de sódio ou ácido clorídrico estava presente. Produtos de maior cristalinidade foram obtidos a partir da síntese, onde o ácido clorídrico foi usado como aditivo.

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Chemistry

Solvothermal Synthesis and Isolation of the Crystalline Material Al-CAU-60

Discovery and Synthesis Optimization of Isoreticular Al(III) Phosphonate-Based Metal-Organic Framework Compounds Using High-Throughput Methods

High-throughput (HT) methods are an important tool for the fast and efficient screening of synthesis parameters and the discovery of new materials. This ...