AN EXPERIMENTAL STUDY OF H₂ AND CO₂ ADSORPTION BEHAVIOR OF C-MOF-5 AND T-MOF-5: A COMPLEMENTARY STUDY

Abstract

In this paper the cubic and tetragonal structure of MOF-5 were successfully synthesized and characterized by TGA and SEM analysis. Equilibrium adsorption isotherms of C-MOF-5 and T-MOF-5 for H₂ and CO₂ were measured up to 25 bar at 298 K using a volumetric method. The C-MOF-5 adsorbent synthesized in this study had a 0.107 and 79.9 wt% adsorption capacities at 298 K and 25 bar for H₂ and CO₂, respectively. T-MOF-5 had a H₂ adsorption capacity of 0.122 wt% and CO₂ adsorption capacity of 67.6 wt% at 298 K and 25 bar. This behavior was attributed to more ZnO units in the T-MOF-5 structure. The difference between H₂ and CO₂ adsorption capacity for the cubic and tetragonal structure of MOF-5, suggests that C-MOF-5 and T-MOF-5 are potential adsorbents for the separation of CO₂ and H₂ from gas mixtures, respectively. Langmuir, Freundlich and Sips isotherm models were used to correlate the adsorption isotherms. The results showed that, at 298 K, the fit of the Sips isotherm to the experimental datawas better than Langmuir and Freundlich isotherms. According to TGA results, the thermal decomposition of C-MOF-5 requires a higher temperature than T-MOF-5.

Keywords:
Adsorption; Hydrogen; Carbon dioxide; MOF-5; ZnO