Automontagem de Metal-Organic Frameworks (MOFs) em escala nanométrica
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Data
2022-11-16
Autores
Rossi, Isabela Fernanda
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Universidade Estadual Paulista (Unesp)
Resumo
As Redes Metalorgânicas (em inglês, Metal-Organic Frameworks ou MOFs) são uma subclasse dos Polímeros de Coordenação. Características como alta cristalinidade, alta área específica, porosidade permanente, baixa densidade e altas estabilidades térmica e química, além da possibilidade de funcionalização, fazem das MOFs um alvo de grande interesse para aplicações em áreas como armazenamento e separação de gases, catálise, fotônica e drug delivery. Em algumas delas é necessário que as MOFs estejam em escala nanométrica e dentro desse contexto, a preparação de nanopartículas uniformes desse tipo de material poroso ainda é um grande desafio. Estratégias como o uso de moduladores de coordenação e/ou a utilização da rota sintética assistida por micro-ondas podem facilitar a formação desses materiais em nanoescala. Assim, esse trabalho propõe investigar o papel de alguns parâmetros de síntese na preparação de nanopartículas do material Eu-MOF, uma MOF luminescente baseada no íon Eu3+ e nos ligantes orgânicos ácido 2-aminotereftálico e 1,10-fenantrolina. Visando, então, um maior controle sobre o tamanho e a morfologia das partículas, os moduladores de coordenação piridina, ácido acético e ácido fórmico, em duas razões modulador/ligante distintas (fator r = 20 e 60), além de duas rotas sintéticas distintas, hidrotérmica convencional e hidrotérmica assistida por micro-ondas, foram utilizados. As partículas relacionadas aos compostos formados utilizando a piridina como modulador apresentaram-se na forma de bastões e em escala nanométrica (entre 64,0 – 400 nm), tanto na síntese pelo aquecimento convencional, quanto na assistida por micro-ondas. Entretanto, o padrão de raios X destes materiais diferem do padrão da MOF sem modulador, indicando a provável formação de uma segunda fase, ainda desconhecida. Já os compostos formados com a utilização dos moduladores ácidos, observou-se através dos espectros FTIR, difratogramas e imagens MEV que, em ambas as rotas sintéticas, há indícios de uma provável mistura entre a fase original do material e uma segunda fase, também desconhecida. Os compostos sintetizados com piridina foram utilizados para a obtenção de filmes que possuem como substrato o PMMA, um polímero inerte. Através de uma análise comparativa entre os espectros de luminescência das amostras na forma de pó e de filmes, o PMMA mostrou-se uma matriz adequada para o suporte das partículas em aplicações onde a utilização da MOF na forma de pó é inviável.
Metal-Organic Frameworks (MOFs) are a subclass of Coordination Polymers. Characteristics such as high crystallinity, high specific area, permanent porosity, low density, and high thermal and chemical stabilities, as well as the possibility of functionalization, make MOFs a target of great interest for applications in some areas, such as storage and separation of gases, catalysis, photonics, and drug delivery. In some of them it is necessary MOFs in nanometer scale, thus the preparation of uniform nanoparticles of this type of porous material is still a challenge. Strategies such as the use of coordination modulators and/or the use of the microwave-assisted synthetic route can facilitate the formation of these materials at the nanoscale. From this perspective, the work proposes to investigate the role of some synthesis parameters in the preparation of nanoparticles of the Eu-MOF material, a luminescent MOF based on the Eu3+ ion and the organic ligands 2-aminoterephthalic acid and 1,10-phenanthroline. Therefore, aiming at greater control over the size and morphology of the particles, the coordination modulators pyridine, acetic acid and formic acid, in two different modulator/ligand ratios (factor r = 20 and 60), in addition to two different synthetic routes, conventional hydrothermal and microwave-assisted hydrothermal, were used. The particles related to the compounds formed using pyridine as modulator were obtained as nanometric rods (between 64,0 - 400 nm), both in conventional heating and microwave synthesis. However, the X-ray pattern of these materials differs from the pattern of the synthesized MOF without modulator, indicating the probable formation of a second phase, which is still unknown. For the compounds formed with the use of acid modulators in both synthetic routes, it was observed via FTIR spectra, diffractograms, and SEM images indications of a probable mixture between the original phase of the material and a second phase, which is also still unknown. The compounds synthesized with pyridine were also used to obtain films that have the inert polymer, PMMA, as substrate. By means of a comparative analysis between the luminescence spectra of the samples in the form of powder and films, PMMA proved to be an adequate matrix for supporting particles in applications where the use of MOF in powder form is unfeasible.
Metal-Organic Frameworks (MOFs) are a subclass of Coordination Polymers. Characteristics such as high crystallinity, high specific area, permanent porosity, low density, and high thermal and chemical stabilities, as well as the possibility of functionalization, make MOFs a target of great interest for applications in some areas, such as storage and separation of gases, catalysis, photonics, and drug delivery. In some of them it is necessary MOFs in nanometer scale, thus the preparation of uniform nanoparticles of this type of porous material is still a challenge. Strategies such as the use of coordination modulators and/or the use of the microwave-assisted synthetic route can facilitate the formation of these materials at the nanoscale. From this perspective, the work proposes to investigate the role of some synthesis parameters in the preparation of nanoparticles of the Eu-MOF material, a luminescent MOF based on the Eu3+ ion and the organic ligands 2-aminoterephthalic acid and 1,10-phenanthroline. Therefore, aiming at greater control over the size and morphology of the particles, the coordination modulators pyridine, acetic acid and formic acid, in two different modulator/ligand ratios (factor r = 20 and 60), in addition to two different synthetic routes, conventional hydrothermal and microwave-assisted hydrothermal, were used. The particles related to the compounds formed using pyridine as modulator were obtained as nanometric rods (between 64,0 - 400 nm), both in conventional heating and microwave synthesis. However, the X-ray pattern of these materials differs from the pattern of the synthesized MOF without modulator, indicating the probable formation of a second phase, which is still unknown. For the compounds formed with the use of acid modulators in both synthetic routes, it was observed via FTIR spectra, diffractograms, and SEM images indications of a probable mixture between the original phase of the material and a second phase, which is also still unknown. The compounds synthesized with pyridine were also used to obtain films that have the inert polymer, PMMA, as substrate. By means of a comparative analysis between the luminescence spectra of the samples in the form of powder and films, PMMA proved to be an adequate matrix for supporting particles in applications where the use of MOF in powder form is unfeasible.
Descrição
Palavras-chave
MOFs, Nanopartículas, Moduladores de coordenação, Síntese hidrotérmica assistida por micro-ondas, Íons lantanídeos