PCM-14 is a dense coordination polymer formed from Ca(II) and an unusual organophosphonium ligand. The dehydrated framework contains 3-coordinate Ca(II) sites within catenated, chiral 3,3-connected nets. PCM-14 exhibits a stark CO(2) sorption selectivity over H(2), N(2) and O(2). The maximum CO(2) uptake was shown to be highly sensitive to the material pretreatment evacuation temperature.