Reversible CO binding enables tunable CO/H2 and CO/N2 separations in metal-organic frameworks with exposed divalent metal cations
Journal
Journal of the American Chemical Society
Journal Volume
136
Journal Issue
30
Pages
10752-10761
Date Issued
2014
Author(s)
Bloch E.D.
Hudson M.R.
Mason J.A.
Chavan S.
Crocell? V.
Howe J.D.
Lee K.
Dzubak A.L.
Queen W.L.
Zadrozny J.M.
Geier S.J.
Lin L.-C.
Gagliardi L.
Smit B.
Neaton J.B.
Bordiga S.
Brown C.M.
Long J.R.
Abstract
Six metal-organic frameworks of the M2(dobdc) (M = Mg, Mn, Fe, Co, Ni, Zn; dobdc4- = 2,5-dioxido-1,4-benzenedicarboxylate) structure type are demonstrated to bind carbon monoxide reversibly and at high capacity. Infrared spectra indicate that, upon coordination of CO to the divalent metal cations lining the pores within these frameworks, the C-O stretching frequency is blue-shifted, consistent with nonclassical metal-CO interactions. Structure determinations reveal M-CO distances ranging from 2.09(2) ? for M = Ni to 2.49(1) ? for M = Zn and M-C-O angles ranging from 161.2(7)° for M = Mg to 176.9(6)° for M = Fe. Electronic structure calculations employing density functional theory (DFT) resulted in good agreement with the trends apparent in the infrared spectra and crystal structures. These results represent the first crystallographically characterized magnesium and zinc carbonyl compounds and the first high-spin manganese(II), iron(II), cobalt(II), and nickel(II) carbonyl species. Adsorption isotherms indicate reversible adsorption, with capacities for the Fe, Co, and Ni frameworks approaching one CO per metal cation site at 1 bar, corresponding to loadings as high as 6.0 mmol/g and 157 cm3/cm3. The six frameworks display (negative) isosteric heats of CO adsorption ranging from 52.7 to 27.2 kJ/mol along the series Ni > Co > Fe > Mg > Mn > Zn, following the Irving-Williams stability order. The reversible CO binding suggests that these frameworks may be of utility for the separation of CO from various industrial gas mixtures, including CO/H2 and CO/N2. Selectivities determined from gas adsorption isotherm data using ideal adsorbed solution theory (IAST) over a range of gas compositions at 1 bar and 298 K indicate that all six M2(dobdc) frameworks could potentially be used as solid adsorbents to replace current cryogenic distillation technologies, with the choice of M dictating adsorbent regeneration energy and the level of purity of the resulting gases. ? 2014 American Chemical Society.
Subjects
Adsorbents
Adsorption isotherms
Binding energy
Carbon monoxide
Cobalt compounds
Crystalline materials
Distillation
Electronic structure
Gas adsorption
Iron compounds
Manganese
Nickel
Positive ions
Spectroscopy
Zinc
Adsorbent regeneration
Cryogenic distillations
Divalent metal cations
Electronic structure calculations
Ideal adsorbed solution theories (IAST)
Industrial gas mixtures
Metal organic framework
Structure determination
Metals
adsorbent
carbon monoxide
carbonyl derivative
cobalt derivative
hydrogen
iron derivative
magnesium derivative
manganese derivative
metal ion
nickel complex
nitrogen
zinc derivative
adsorption
article
binding affinity
calculation
chemical binding
chemical composition
chemical interaction
chemical structure
crystal structure
density functional theory
dissociation
distillation
gas
infrared spectroscopy
structure analysis
temperature dependence
Type
journal article