Comparative Study of the Adsorption Equilibrium of CO₂ on Microporous Commercial Materials at Low Pressures

The adsorption of CO₂ on several microporous materials has been measured at various temperatures (263, 273, 283, and 293 K) over a wide range of pressures. The porous materials studied were three zeolites (5A, 13A, and 13X), two metal–organic frameworks (Basolite A100 and Basolite Z1200), an activated carbon, and two pillared clays (Al-PILC and Zr-PILC). The data obtained were fitted to the Freundlich, Langmuir, and Toth isotherms. Various methods were used to calculate the Henry’s law constants. The values found for the zeolites, which ranged from 8.95 to 36.02 mmol/kPa·g at 273 K, were much higher than those for the metal–organic frameworks, activated carbon, and pillared clays, which ranged from 0.012 to 0.200 mmol/kPa·g at the same temperature. The isosteric heats of adsorption of CO₂ on the materials were calculated using the Clausius–Clapeyron equation, and the adsorbent–CO₂ affinity was found to increase in the order Z1200 ≈ 13X ≈ 13A < 5A < Zr-PILC < A100 ≈ AC ≈ Al-PILC at low loadings.