where V pore frame (m 3 kg -1 ) is the probe-occupiable accessible pore volume of the crystal structure and can be computed from the crystal structure by Zeo ++ . For the liquid densities of the guest molecules, we used 25.02 and 28.84 (mol m -3 ) for CO 2 and N 2 , respectively. By substituting equation 8 into equation 7 we can compute P sat using: