where pn (n = 1 or 2) denotes the pressure value for the n th isotherm; Tn (n = 1 or 2) denotes the temperature value for the n th isotherm; R is the gas constant expressed in the appropriate units (8.314 J K -1 mol -1 ). To evaluate the CO2/N2 selectivity at 25 °C, the N2 adsorption isotherms were acquired at 25 °C and up to 1.2 bar. The CO2/N2 Henry selectivity was calculated as the ratio of the initial slopes of the two adsorption isotherms in the 0.01  p  0.1 bar range. The CO2/N2 ideal adsorbed solution theory (IAST) selectivity of binary mixtures at a total pressure of 1 bar and at T = 25 °C was determined as the ratio of the adsorbed molar fractions of the two gases divided by the ratio of the gas phase initial molar fractions: 47