Περίληψη:
The synthesis and characterization of [Co-9(INA)(18)(H2O)(6)]center
dot 11DMF center dot 15H(2)O(8) (Co-9-INA center dot 11DMF center dot
15H(2)O) (INA(-) = the anion of isonicotinic acid) is reported. It
exhibits a rigid 3D-porous structure with a Co-9 repeating unit
consisting of four [Co-2(II)(mu-O2CR)(2)(mu-H2O)] subunits (two
unique) linked through bridging INA(-) ligands to an isolated Co-II ion
(half unique). The [Co-2(II)] dimers and the isolated Co-II ion have
assembled to create a trinodal (6,7,8)-coordinated network with point
symbol
(3(2).4(11).5(6).6(2))(2)(3(2).4(18).5(4).6(4))(2)(3(4).4(4).5(4).6(3)).
Gas sorption studies revealed that Co-9-INA exhibits 910 m(2) g(-1) BET
area, 4.2 mmol g(-1) CO2 uptake at 273 K/1 bar, and 6.7 CO2/CH4
selectivity at zero coverage. Furthermore, Co-9-INA displays capability
for exchange of the guest solvent molecules by various organic molecules
in a single-crystal to single-crystal fashion. Direct and alternating
current magnetic susceptibility studies revealed the existence of
dominant antiferromagnetic interactions between the Co2+ ions that
result in a paramagnetic ST = 3/2 spin ground state value. Overall, this
work emphasizes the potential of relatively simple and inexpensive
polytopic ligands, such as isonicotic acid, to stabilize microporous
MOFs with significant CO2 sorption capacity.
