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Synthesis and Characterization of Functionalized Metal-organic Frameworks
Published on: September 5, 2014
Interacciones específicas del metal del H2 adsorbido dentro de los marcos isostruturales metal-orgánicos
Stephen A FitzGerald1, Brian Burkholder, Michael Friedman
1Department of Physics and Astronomy, Oberlin College, Oberlin, Ohio 44074, USA. stephen.fitzgerald@oberlin.edu
Journal of the American Chemical Society
|November 15, 2011
Resumen
La espectroscopia infrarroja revela cómo las moléculas de hidrógeno (H) se unen a sitios metálicos en marcos orgánicos metálicos (MOF). Este estudio aclara los mecanismos de adsorción de H2+, refutando una teoría reciente que involucra fuertes interacciones H2+.
Área de la Ciencia:
- Ciencia de los materiales Ciencia de los materiales.
- La espectroscopia es una técnica de espectroscopia.
- Química Física es la química física.
Sus antecedentes:
- Los marcos metálico-orgánicos (MOF), específicamente MOF-74 y CPO-27, se investigan por sus propiedades de adsorción de gases.
- Comprender la adsorción de hidrógeno en los MOF es crucial para las aplicaciones en el almacenamiento y la separación de gases.
Objetivo del estudio:
- Para investigar la dinámica y los sitios de unión del hidrógeno (H) adsorbido dentro de M (M = Mg, Mn, Co, Ni, Zn) MOFs utilizando espectroscopía infrarroja de reflexión difusa.
- Para aclarar el mecanismo de adsorción de H(2) en estos materiales y evaluar los modelos existentes.
Principales métodos:
- La espectroscopia de reflexión difusa infrarroja (IR) se realizó en un rango de temperatura de 35-298 K.
- La adsorción de H2 fue estudiada en diferentes concentraciones (0,1 a 3,0 H2 por catión metálico).
- Se analizaron espectros para identificar modos vibratorios y sus cambios, correlacionándolos con sitios de adsorción y entalpias.
Principales resultados:
- Los modos vibratorios fuertemente desplazados hacia el rojo indican H2 aislado unido a sitios de coordinación metálicos.
- El grado de desplazamiento al rojo se correlaciona con las entalpías isostéricas de adsorción, que varían con la identidad del metal (M).
- H(2) adsorbido lejos de los sitios metálicos mostró diferencias espectrales mínimas a través de los MOF estudiados.
- Las características espectrales observadas solo se reproducen en muestras contaminadas, no en MOF puros.
Conclusiones:
- Los hallazgos apoyan un mecanismo de adsorción gradual en sitios de marco discretos, consistente con los modelos anteriores.
- El estudio refuta un mecanismo propuesto recientemente que involucra fuertes interacciones H.
- Los desplazamientos espectrales sistemáticos de los isotopólogos y las bandas de sobretono de H(2) apoyan aún más el modelo de adsorción propuesto.
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