Probing the Adsorption Sites for CO2 in Metal Organic Frameworks Materials MIL-53 (Al, Cr) and MIL-47 (V) by Density Functional Theory
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- 作者：N. A. Ramsahye ; G. Maurin ; S. Bourrelly ; P. L. Llewellyn ; C. Serre ; T. Loiseau ; T. Devic ; G. Fé ; rey
- 刊名：Journal of Physical Chemistry C
- 出版年：2008
- 出版时间：January 17, 2008
- 年：2008
- 卷：112
- 期：2
- 页码：514 - 520
- 全文大小：439K
- 年卷期：v.112,no.2(January 17, 2008)
- ISSN：1932-7455
文摘
A comprehensive DFT study of the possible CO2 adsorption geometries in the MIL-53 (Al, Cr) and MIL-47hybrid organic-inorganic materials has been performed, as a preliminary step to gain a deeper understandingof the CO2 adsorption mechanism in these systems and to help explain the "breathing" effect displayed bythe MIL-53 materials. This technique allows us to explore the possible spatial configurations of the CO2molecules in the MIL-53 systems depending on the size of the pore opening at different loadings. Our resultsshow that the replacement of the 
f">2-OH groups by oxo moieties in the MIL-47 material leads to fewer,weaker adsorption sites for CO2 onto the framework itself, whereas a larger number of CO2 geometries arepossible in both the large and narrow versions of MIL-53. In the narrow pore form, the double interaction,where a CO2 molecule bridges the pore to simultaneously coordinate with 2 f">2-OH groups on opposite sidesof a pore wall, was predicted to be the most energetic arrangement at the initial stage of adsorption. Additionalconfigurations include coordination with both inorganic and organic parts of the framework. When the numberof CO2 molecule increases, our calculations indicate that the resulting increase in the intermolecular interactionsbetween the adsorbate molecules lead to a significant modification of the CO2 arrangement within the poreand should be an important feature in the explanation of the "breathing" of this material. In the large poreform, an interaction reflecting the opening of the pore is not possible, and so the most likely interaction isone where a CO2 interacts with a single f">2-OH group, in a number of different orientations.
f">2-OH groups by oxo moieties in the MIL-47 material leads to fewer,weaker adsorption sites for CO2 onto the framework itself, whereas a larger number of CO2 geometries arepossible in both the large and narrow versions of MIL-53. In the narrow pore form, the double interaction,where a CO2 molecule bridges the pore to simultaneously coordinate with 2 f">2-OH groups on opposite sidesof a pore wall, was predicted to be the most energetic arrangement at the initial stage of adsorption. Additionalconfigurations include coordination with both inorganic and organic parts of the framework. When the numberof CO2 molecule increases, our calculations indicate that the resulting increase in the intermolecular interactionsbetween the adsorbate molecules lead to a significant modification of the CO2 arrangement within the poreand should be an important feature in the explanation of the "breathing" of this material. In the large poreform, an interaction reflecting the opening of the pore is not possible, and so the most likely interaction isone where a CO2 interacts with a single f">2-OH group, in a number of different orientations.