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Title: Selective Binding of O(2) over N(2) in a Redox-Active Metal-Organic Framework with Open Iron(II) Coordination Sites
Authors: Bloch, ED
Murray, LJ
Queen, WL
Chavan, S
Maximoff, SN
Bigi, JP
Krishna, R
Peterson, VK
Grandjean, F
Long, GJ
Smit, B
Bordiga, S
Brown, CM
Long, JR
Keywords: Hydrogen
Crystal structure
Neutron diffraction
Issue Date: 21-Sep-2011
Publisher: American Chemical Society
Citation: Bloch, E. D., Murray, L .J., Queen, W. L., Chavan, S., Maximoff, S. N., Bigi, J. P., Krishna, R., Peterson, V. K., Grandjean, F., Long, G. J., Smit, B., Bordiga, S., Brown, C. M., & Long, J. R. (2011). Selective binding of O(2) over N(2) in a redox-active metal-organic framework with open iron(II) coordination sites, Journal of the American Chemical Society, 133(37), 14814-14822. doi:10.1021/ja205976v
Abstract: The air-free reaction between FeCl2 and H4dobdc (dobdc4– = 2,5-dioxido-1,4-benzenedicarboxylate) in a mixture of N,N-dimethylformamide (DMF) and methanol affords Fe2(dobdc)·4DMF, a metal–organic framework adopting the MOF-74 (or CPO-27) structure type. The desolvated form of this material displays a Brunauer–Emmett–Teller (BET) surface area of 1360 m2/g and features a hexagonal array of one-dimensional channels lined with coordinatively unsaturated FeII centers. Gas adsorption isotherms at 298 K indicate that Fe2(dobdc) binds O2 preferentially over N2, with an irreversible capacity of 9.3 wt %, corresponding to the adsorption of one O2 molecule per two iron centers. Remarkably, at 211 K, O2 uptake is fully reversible and the capacity increases to 18.2 wt %, corresponding to the adsorption of one O2 molecule per iron center. Mössbauer and infrared spectra are consistent with partial charge transfer from iron(II) to O2 at low temperature and complete charge transfer to form iron(III) and O22– at room temperature. The results of Rietveld analyses of powder neutron diffraction data (4 K) confirm this interpretation, revealing O2 bound to iron in a symmetric side-on mode with dO–O = 1.25(1) Ã… at low temperature and in a slipped side-on mode with dO–O = 1.6(1) Ã… when oxidized at room temperature. Application of ideal adsorbed solution theory in simulating breakthrough curves shows Fe2(dobdc) to be a promising material for the separation of O2 from air at temperatures well above those currently employed in industrial settings. © 2011, American Chemical Society
Gov't Doc #: 3784
ISSN: 0002-7863
Appears in Collections:Journal Articles

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