Selective Binding of O2 over N2 in a Redox鈥揂ctive Metal鈥揙rganic Framework with Open Iron(II) Coordination Sites
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- 作者：Eric D. Bloch ; Leslie J. Murray ; Wendy L. Queen ; Sachin Chavan ; Sergey N. Maximoff ; Julian P. Bigi ; Rajamani Krishna ; Vanessa K. Peterson ; Fernande Grandjean ; Gary J. Long ; Berend Smit ; Silvia Bordiga ; Craig M. Brown ; Jeffrey R. Long
- 刊名：Journal of the American Chemical Society
- 出版年：2011
- 出版时间：September 21, 2011
- 年：2011
- 卷：133
- 期：37
- 页码：14814-14822
- 全文大小：1012K
- 年卷期：v.133,no.37(September 21, 2011)
- ISSN：1520-5126
文摘
The air-free reaction between FeCl2 and H4dobdc (dobdc4鈥?/sup> = 2,5-dioxido-1,4-benzenedicarboxylate) in a mixture of N,N-dimethylformamide (DMF) and methanol affords Fe2(dobdc)路4DMF, a metal鈥搊rganic framework adopting the MOF-74 (or CPO-27) structure type. The desolvated form of this material displays a Brunauer鈥揈mmett鈥揟eller (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. M枚ssbauer 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鈥?/sup> 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鈥揙 = 1.25(1) 脜 at low temperature and in a slipped side-on mode with dO鈥揙 = 1.6(1) 脜 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.