Structural Stability of Metal Organic Framework MOF-177

The Journal of Physical Chemistry Letters 11/2009; 1(1). DOI: 10.1021/jz900028u

ABSTRACT Metal organic framework MOF-177 is one of the most promising crystalline porous adsorbents for hydrogen adsorption. The effects of oxygen and water on the structural stability of MOF-177 are investigated by X-ray diffraction (XRD) and thermogravimetric analysis (TGA). A MOF-177 sample is exposed to ambient air for 5 weeks and monitored for its structural changes by XRD. The crystal structure of MOF-177 gradually changes from hexagonal to orthogonal, and then to monoclinic in the 5-week period. The crystal structure of MOF-177 is completely destroyed after it is immersed in water. The weight loss of MOF-177 is negligible at temperatures below 330 °C in the presence of oxygen. However, MOF-177 totally converts to zinc oxide at 420 °C.Keywords (keywords): MOF-177; structural stability; XRD; TGA; crystal structure

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    ABSTRACT: Adsorption of volatile organic compounds (VOCs) including acetone, benzene, toluene, ethylbenzene, o-xylene, m-xylene, p-xylene and ethenylbenzene in air on a synthesized MOF-177 and the influence of humidity on adsorption were examined at 25 ± 0.5 °C. Larger adsorption capacity of VOCs on MOF-177 was observed even at relatively high humidity, suggesting that the porous MOF-177 material could be a potential adsorbent for sorptive removal of the unwanted VOCs from air due to its large surface area and pore volume. Adsorption of VOCs on MOF-177 is captured by a pore filling mechanism, showing a negative linear relationship between the volume adsorption capacity and the molecular cross-sectional area of VOCs. Adsorption of VOCs on MOF-177 in humid air will be suppressed by the competition of water molecules and the decomposition of MOF-177 framework structure with water. It was suggested that MOF-177 should not be exposed a long time to air at relatively high RH and pre-drying of gas is required to avoid the competition suppress of water on adsorption and the decomposition of MOF-177 framework structure in the applications of MOF-177 as adsorbents.
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