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 CMOF- 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.

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