Carbon dioxide adsorption in microwave-synthesized metal organic framework CPM-5: Equilibrium and kinetics study

Abstract

The adsorption equilibrium and diffusion of CO2 in CPM-5 (crystalline porous materials) were experimentally studied using a volumetric approach at three different temperatures 273, 298, and 318K and gas pressures up to 105kPa. The Freundlich adsorption equilibrium model was applied to correlate the adsorption isotherms, and the classical microspore diffusion model was applied to obtain the adsorption kinetic curves and diffusivity of CO2 in CPM-5. The selectivity of CO2 over N2 was estimated from the single component isotherms at conditions relevant to post combustion applications (0.15bar PCO2 and 0.75bar pN2). It was found that at pressures up to 105kPa, the CPM-5 adsorbent has CO2 adsorption capacity of 3mmol/g, 2.3mmol/g, at 273K and 298K, respectively, which is significantly higher than those of MOF-5 under the same conditions. The selectivity factor was 14.2 and 16.1 at 273 and 298K, respectively. The CO2 diffusivity in CPM-5, estimated from the adsorption kinetic data measured at low pressures, are 1.86×10−12m2/s, 7.04×10−12m2/s, and 7.87×10−12m2/s at 273K, 298K and 318K, respectively. The initial isosteric heat of adsorption of CO2 on the CPM-5 is 36.1kJ/mol. CPM-5 shows attractive adsorption properties as an adsorbent for separation of CO2 from flue gas.