Highly Selective Carbon Dioxide Uptake by [Cu(bpy-n)2(SiF6)] (bpy-1 = 4,4′-Bipyridine; bpy-2 = 1,2-Bis(4-pyridyl)ethene)

A previously known class of porous coordination polymer (PCP) of formula [Cu­(bpy-n)2(SiF6)] (bpy-1 = 4,4′-bipyridine; bpy-2 = 1,2-bis­(4-pyridyl)­ethene) has been studied to assess its selectivity toward CO2, CH4, N2, and H2O. Gas sorption measurements reveal that [Cu­(bpy-1)2(SiF6)] exhibits the highest uptake for CO2 yet seen at 298 K and 1 atm by a PCP that does not contain open metal sites. Significantly, [Cu­(bpy-1)2(SiF6)] does not exhibit particularly high uptake under the same conditions for CH4, N2, and, H2O, presumably because of its lack of open metal sites. Consequently, at 298 K and 1 atm [Cu­(bpy-1)2(SiF6)] exhibits a relative uptake of CO2 over CH4 of ca. 10.5:1, the highest value experimentally observed in a compound without open metal sites. [Cu­(bpy-2)2(SiF6)] exhibits larger pores and surface area than [Cu­(bpy-1)2(SiF6)] but retains a high CO2/CH4 relative uptake of ca. 8:1.