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La sensibilidad al agua en los MOFs basados en Zn4O depende de la estructura y el historial
Ping Guo1, Dhanadeep Dutta, Antek G Wong-Foy
1Department of Chemistry, University of Michigan , 930 N. University, Ann Arbor, Michigan 48109-1055, United States.
Journal of the American Chemical Society
|February 3, 2015
Resumen
Las estructuras metal-orgánicas (MOF) muestran una sorprendente estabilidad contra la humedad, con un período de inducción inicial antes de que se produzca la degradación. Este estudio revela la evolución del tamaño de los poros de MOF durante el colapso estructural inducido por el agua.
Área de la Ciencia:
- Ciencia de los materiales Ciencia de los materiales.
- Química Química es la química.
- Nanotecnología La nanotecnología es la nanotecnología.
Sus antecedentes:
- La humedad causa un colapso estructural irreversible en las estructuras metal-orgánicas (MOF), reduciendo su superficie interna y el volumen de poros.
- Los mecanismos precisos y la evolución del tamaño de los poros durante la degradación de MOF por la humedad no se comprenden bien debido a las limitaciones en la sonda de porosidad in situ.
Objetivo del estudio:
- Para investigar la evolución dinámica del tamaño de los poros y los mecanismos de degradación de los MOF bajo exposición a la humedad.
- Para identificar los factores que influyen en la estabilidad de MOF y la cinética de degradación.
Principales métodos:
- Utilizó un sistema de flujo continuo combinado con espectroscopia de aniquilación de positronio in situ (PALS) para monitorear dinámicamente la porosidad de MOF.
- Se emplearon mediciones de difracción de rayos X de polvo (PXRD) y mediciones de adsorción de gas ex situ para mayor verificación.
Principales resultados:
- Se observó un período de inducción inesperado para la degradación del agua en algunos MOF basados en Zn4O, lo que indica una mayor estabilidad de lo que se suponía anteriormente.
- Caracterizó una tendencia de degradación sigmoidal en MOFs no funcionales, vinculada a la evolución del tamaño del poro temporal.
- El IRMOF-3 exhibió una humedad relativa de degradación más baja que el MOF-5, con porosidad residual en el IRMOF-3.
- Demostración de la dependencia histórica del período de inducción de la exposición previa al agua.
Conclusiones:
- El estudio revela una estabilidad previamente no reconocida en ciertos MOF contra la humedad, caracterizada por un período de inducción inicial.
- In situ PALS proporciona información crucial sobre la evolución temporal de la porosidad de MOF durante la degradación inducida por la humedad.
- Comprender los mecanismos de degradación de MOF, incluida la dependencia de la historia y el comportamiento sigmoidal, es vital para su aplicación en entornos húmedos.
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