A Microporous Co2+ Metal Organic Framework with Single-Crystal to Single-Crystal Transformation Properties and High CO2 Uptake

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.