Structural and Selective Gas Adsorption Studies of Polyoxometalate and Tris(ethylenediamine) Cobalt(III) Based Ionic Crystals

Seven new ionic solids built on polyoxometalate anions and [Co(en)(3)](3+) cations, namely, [Co(en)(3)Mo8O26(H3O)-(Cl)](DMF)(4)(H2O) (Co-Mo-8-DMF), [alpha-PW12O40][Co(en)(3)]center dot 6DMF (Co-W12P-DMF), [alpha-PW12O40][Co(en)(3)]center dot 6DEF (Co-W12P-DEF), [alpha-PMo12O40][Co(en)(3)]center dot 5.5DMF (Co-Mo12P-DMF), [alpha-PMo12O40][Co(en)(3)]center dot 6DEF (Co-Mo12P-DEF), [alpha-SiW12O40]-[Co(en)(3)](3/2)[Cl](1/2)center dot 6DMF center dot 3H(2)O (Co-W12Si-DMF), and [alpha-SiW12O40][Co(en)(3)]center dot 6DEF (Co-W12Si-DEF), have been synthesized from nonaqueous (DMF/DEF) media and characterized by single-crystal X-ray diffraction. We attempt to understand if [Co(en)(3)](3+) cations used in these reaction systems play a crucial role in controlling the assembly of these crystals. These ionic solids, after removal of the DMF or DEF molecules, are found to exhibit size selective H-2 adsorption properties over N-2. The amount of hydrogen adsorption was influenced by POM anion types and their orientations. CoMo12P-DEF has the highest (0.9 wt %) H-2 uptake, and CoW12P-DEF has the lowest (0.4 wt %) uptake among the series when the adsorbate pressure approached 1 atm.