Síntese ambientalmente segura do IRMOF-3: uma proposta aplicando o método mecanoquímico
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Data
2023-03-03
Autores
Isquibola, Guilherme
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Editor
Universidade Estadual Paulista (Unesp)
Resumo
As estruturas metalorgânicas (MOF) são compostos emergentes que tem ganhado elevado destaque nas ciências de materiais por conta de diversos fatores, tal como a presença de poros em sua estrutura, que possibilitam seu uso nos mais vastos campos de aplicação, como para o delivery de medicamentos, sensoriamento de gases, estocagem de combustíveis e em diversas outras áreas de estudo. Usualmente, tais estruturas são sintetizadas por método solvotérmico, que utiliza de solventes com alto ponto de ebulição, mantidos por horas em um reator que gera um ambiente com elevada pressão, facilitando os processos de nucleação. No entanto, o uso de solventes tóxicos e o tempo de produção tornam a síntese solvotérmica pouco atrativa em um contexto ambiental, incentivando a busca e aplicação de novos métodos que atendam aos preceitos formulados pela química verde. Neste sentido, os métodos mecanoquímicos surgem como uma alternativa para se alcançar a produção de MOFs sob condições ambientalmente seguras. A mecanoquímica ocorre pela moagem dos reagentes, condição que enfraquece ligações e favorece a formação de novas, em abordagens conhecidas por moagem pura (neat grinding, NG) e moagem assistida por líquido (liquid assisted grinding, LAG). Assim, esse trabalho objetivou o desenvolvimento e a exploração da síntese verde do IRMOF-3 por métodos mecanoquímicos via NG e LAG. As variáveis que interferem em um processo mecanoquímico e que foram estudadas no trabalho foram a fonte de zinco, proporção metal:ligante, tempo de síntese, frequência e o volume de solvente. A condição de síntese mecanoquímica que apresentou os melhores resultados da otimização foi com o uso de acetato de zinco como fonte de metal, abordagem LAG com adição de 5 mL de dimetilformamida, em uma proporção metal:ligante 1:3 sob um tempo de moagem de 60 minutos a 18,3 Hz de frequência. Os compostos produzidos via síntese mecanoquímica (LAG e NG) foram de alta pureza (superior a 99%), dados comprovados por meio de técnica termoanalítica (TG/DSC), espectroscópicas (FTIR/EGA), difração de raios-X por método e pó e por análises de adsorção de nitrogênio. O composto produzido via síntese mecanoquímica teve suas propriedades físico-química comparáveis com aquele produzido por método convencional, validando a proposta de síntese mecanoquímica do IRMOF-3.
Metalorganic frameworks (MOF) are emerging compounds that have gained high prominence in materials science due to several factors, such as the presence of pores in their structure, which enable their use in the widest fields of application, such as for the delivery of medicines, gas sensing, fuel storage and in several other areas of study. Usually, such structures are synthesized by the solvothermal method, which uses solvents with a high boiling point, kept for hours in a reactor that generates an environment with high pressure, facilitating the nucleation processes. However, the use of toxic solvents and the production time make solvothermal synthesis unattractive in an environmental context, encouraging the search and application of new methods that meet the precepts formulated by green chemistry. In this sense, mechanochemical methods emerge as an alternative to achieve the production of MOFs under environmentally safe conditions. Mechanochemistry occurs by grinding the reagents, a condition that weakens bonds and favors the formation of new ones, in approaches known as neat grinding (NG) and liquid-assisted grinding (LAG). Thus, this work aimed to develop and explore the green synthesis of IRMOF-3 by mechanochemical methods via NG and LAG. The variables that interfere in a mechanochemical process and that were studied in the work were the zinc source, metal:linker ratio, synthesis time, frequency, and volume of solvent. The mechanochemical synthesis condition that presented the best optimization results was with the use of zinc acetate as a metal source, LAG approach with the addition of 5 mL of dimethylformamide, in a metal:binder ratio 1:3 under a milling time of 60 minutes at 18.33 Hz frequency. The compounds produced via mechanochemical synthesis (LAG and NG) were of high purity (over 99%), data confirmed by means of thermoanalytical techniques (TG/DSC), spectroscopic (FTIR/EGA), X-ray diffraction by method and powder and by nitrogen adsorption analyses. The compound produced via mechanochemical synthesis had its physicochemical properties comparable to that produced by conventional method, validating the proposed mechanochemical synthesis of IRMOF-3.
Metalorganic frameworks (MOF) are emerging compounds that have gained high prominence in materials science due to several factors, such as the presence of pores in their structure, which enable their use in the widest fields of application, such as for the delivery of medicines, gas sensing, fuel storage and in several other areas of study. Usually, such structures are synthesized by the solvothermal method, which uses solvents with a high boiling point, kept for hours in a reactor that generates an environment with high pressure, facilitating the nucleation processes. However, the use of toxic solvents and the production time make solvothermal synthesis unattractive in an environmental context, encouraging the search and application of new methods that meet the precepts formulated by green chemistry. In this sense, mechanochemical methods emerge as an alternative to achieve the production of MOFs under environmentally safe conditions. Mechanochemistry occurs by grinding the reagents, a condition that weakens bonds and favors the formation of new ones, in approaches known as neat grinding (NG) and liquid-assisted grinding (LAG). Thus, this work aimed to develop and explore the green synthesis of IRMOF-3 by mechanochemical methods via NG and LAG. The variables that interfere in a mechanochemical process and that were studied in the work were the zinc source, metal:linker ratio, synthesis time, frequency, and volume of solvent. The mechanochemical synthesis condition that presented the best optimization results was with the use of zinc acetate as a metal source, LAG approach with the addition of 5 mL of dimethylformamide, in a metal:binder ratio 1:3 under a milling time of 60 minutes at 18.33 Hz frequency. The compounds produced via mechanochemical synthesis (LAG and NG) were of high purity (over 99%), data confirmed by means of thermoanalytical techniques (TG/DSC), spectroscopic (FTIR/EGA), X-ray diffraction by method and powder and by nitrogen adsorption analyses. The compound produced via mechanochemical synthesis had its physicochemical properties comparable to that produced by conventional method, validating the proposed mechanochemical synthesis of IRMOF-3.
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Palavras-chave
Complexos metálicos, Análise térmica, Síntese, Moagem, Compostos de zinco