微型多孔材料
结晶度
颗粒
相对湿度
湿度
重量分析
化学工程
金属有机骨架
吸附
解吸
材料科学
降级(电信)
化学
复合材料
热力学
有机化学
物理
工程类
计算机科学
电信
作者
Ming Yang,Justin Purewal,Jun Yang,Chunchuan Xu,R.E. Soltis,James R. Warner,Mike Veenstra,Manuela Gaab,Ulrich Müller,Donald J. Siegel
出处
期刊:Langmuir
[American Chemical Society]
日期:2015-04-21
卷期号:31 (17): 4988-4995
被引量:88
标识
DOI:10.1021/acs.langmuir.5b00833
摘要
Metal-organic frameworks (MOFs) are an emerging class of microporous, crystalline materials with potential applications in the capture, storage, and separation of gases. Of the many known MOFs, MOF-5 has attracted considerable attention because of its ability to store gaseous fuels at low pressure with high densities. Nevertheless, MOF-5 and several other MOFs exhibit limited stability upon exposure to reactive species such as water. The present study quantifies the impact of humid air exposure on the properties of MOF-5 as a function of exposure time, humidity level, and morphology (i.e., powders vs pellets). Properties examined include hydrogen storage capacity, surface area, and crystallinity. Water adsorption/desorption isotherms are measured using a gravimetric technique; the first uptake exhibits a type V isotherm with a sudden increase in uptake at ∼50% relative humidity. For humidity levels below this threshold only minor degradation is observed for exposure times up to several hours, suggesting that MOF-5 is more stable than generally assumed under moderately humid conditions. In contrast, irreversible degradation occurs in a matter of minutes for exposures above the 50% threshold. Fourier transform infrared spectroscopy indicates that molecular and/or dissociated water is inserted into the skeletal framework after long exposure times. Densification into pellets can slow the degradation of MOF-5 significantly, and may present a pathway to enhance the stability of some MOFs.
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