Molecular understanding for the adsorption of water and alcohols in hydrophilic and hydrophobic zeolitic metal-organic frameworks

Nalaparaju, A, Zhao, X. S. and Jiang, J. W. (2010) Molecular understanding for the adsorption of water and alcohols in hydrophilic and hydrophobic zeolitic metal-organic frameworks. Journal of Physical Chemistry C, 114 26: 11542-11550. doi:10.1021/jp1033273


Author Nalaparaju, A
Zhao, X. S.
Jiang, J. W.
Title Molecular understanding for the adsorption of water and alcohols in hydrophilic and hydrophobic zeolitic metal-organic frameworks
Journal name Journal of Physical Chemistry C   Check publisher's open access policy
ISSN 1932-7447
1932-7455
Publication date 2010-07
Sub-type Article (original research)
DOI 10.1021/jp1033273
Volume 114
Issue 26
Start page 11542
End page 11550
Total pages 9
Place of publication Washington, DC United States Publisher
Publisher American Chemical Society
Language eng
Formatted abstract
A molecular simulation study is reported for the adsorption of water and alcohols (methanol and ethanol) in two metal-organic frameworks (MOFs) topologically similar to rho-zeolite; one is a hydrophilic Na +-exchanged rho-zeolite-like MOF (Na-rho-ZMOF), and the other is a hydrophobic zeolitic-imidazolate framework-71 (ZIF-71). The adsorption isotherms in Na-rho-ZMOF are type I as a consequence of the high affinity of the nonframework Na+ ions and ionic framework. The adsorption capacity decreases in the order of water > methanol > ethanol. Water is adsorbed more closely in the window region, whereas methanol and ethanol are populated in the α cage due to steric effect. In water/methanol and water/ethanol mixtures, water adsorption increases continuously with increasing pressure and replaces alcohols competitively at high pressures. In ZIF-71, the framework-adsorbate affinity is relatively weaker and type V adsorption is observed. Water has vanishingly small adsorption at low pressures and a sharp increase in adsorption at 22 kPa due to capillary condensation. Methanol and ethanol exhibit cluster-growth adsorption, followed by continuous pore filling. The adsorption in ZIF-71 increases in the order of water < methanol < ethanol at low pressures; however, the opposite order is observed at high pressures because of entropy effect. In water/alcohol mixtures, alcohols are selectively more adsorbed at low pressures but surpassed by water with increasing pressure. The framework charges have a substantial effect on adsorption in Na-rho-ZMOF, but not in ZIF-71. This study provides a molecular understanding for the adsorption of water and alcohols in two zeolitic MOFs with the identical topology and reveals the significantly different adsorption mechanisms. © 2010 American Chemical Society.
Keyword Imidazolate Frameworks
Methanol Mixtures
Carbon-Dioxide
Dynamics Simulations
Selective Adsorption
Hydrogen Storage
Gas
Separation
Co2
Naa
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status Unknown

Document type: Journal Article
Sub-type: Article (original research)
Collections: School of Chemical Engineering Publications
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