Highly Selective Carbon Dioxide Uptake by [Cu(bpy-<i>n</i>)<sub>2</sub>(SiF<sub>6</sub>)] (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-<i>n</i>)<sub>2</sub>(SiF<sub>6</sub>)] (bpy-1 = 4,4′-bipyridine; bpy-2 = 1,2-bis­(4-pyridyl)­ethene) has been studied to assess its selectivity toward CO<sub>2</sub>, CH<sub>4</sub>, N<sub>2</sub>, and H<sub>2</sub>O. Gas sorption measurements reveal that [Cu­(bpy-1)<sub>2</sub>(SiF<sub>6</sub>)] exhibits the highest uptake for CO<sub>2</sub> yet seen at 298 K and 1 atm by a PCP that does not contain open metal sites. Significantly, [Cu­(bpy-1)<sub>2</sub>(SiF<sub>6</sub>)] does not exhibit particularly high uptake under the same conditions for CH<sub>4</sub>, N<sub>2</sub>, and, H<sub>2</sub>O, presumably because of its lack of open metal sites. Consequently, at 298 K and 1 atm [Cu­(bpy-1)<sub>2</sub>(SiF<sub>6</sub>)] exhibits a relative uptake of CO<sub>2</sub> over CH<sub>4</sub> of <i>ca</i>. 10.5:1, the highest value experimentally observed in a compound without open metal sites. [Cu­(bpy-2)<sub>2</sub>(SiF<sub>6</sub>)] exhibits larger pores and surface area than [Cu­(bpy-1)<sub>2</sub>(SiF<sub>6</sub>)] but retains a high CO<sub>2</sub>/CH<sub>4</sub> relative uptake of <i>ca</i>. 8:1.