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J Phys Chem Lett. 2015 May 21;6(10):1790-4. doi: 10.1021/acs.jpclett.5b00440. Epub 2015 Apr 30.

Understanding the Adsorption Mechanism of Xe and Kr in a Metal-Organic Framework from X-ray Structural Analysis and First-Principles Calculations.

Author information

1
†National Synchrotron Light Source II, Brookhaven National Laboratory, Upton, New York 11973, United States.
2
‡Computational Science Center, Brookhaven National Laboratory, Upton, New York 11973, United States.
3
§X-ray Science Division, Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, United States.
4
∥Mineral Physics Institute, Stony Brook University, Stony Brook, New York 11794, United States.
5
⊥Department of Nuclear Science and Technology, Brookhaven National Laboratory, Upton, New York 11973, United States.
6
#Deutsches Elektronen-Synchrotron DESY, D-22607, Hamburg, Germany.
7
∇DM Strachan, LLC, Bend, Oregon 97707, United States.
8
○Energy and Environment Directorate, Pacific Northwest National Laboratory, Richland, Washington 99352, United States.

Abstract

Enhancement of adsorption capacity and separation of radioactive Xe/Kr at room temperature and above is a challenging problem. Here, we report a detailed structural refinement and analysis of the synchrotron X-ray powder diffraction data of Ni-DODBC metal organic framework with in situ Xe and Kr adsorption at room temperature and above. Our results reveal that Xe and Kr adsorb at the open metal sites, with adsorption geometries well reproduced by DFT calculations. The measured temperature-dependent adsorption capacity of Xe is substantially larger than that for Kr, indicating the selectivity of Xe over Kr and is consistent with the more negative adsorption energy (dominated by van der Waals dispersion interactions) predicted from DFT. Our results reveal critical structural and energetic information about host-guest interactions that dictate the selective adsorption mechanism of these two inert gases, providing guidance for the design and synthesis of new MOF materials for the separation of environmentally hazardous gases from nuclear reprocessing applications.

KEYWORDS:

X-ray diffraction; density functional calculations; metal−organic frameworks; noble gases; van der Waals interactions

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