Adsorption of CO2, CO, CH4 and N2 on a zinc based metal organic framework

In this work, we report the gas adsorption properties of a zinc based metal organic framework, (Zn-2(bdc)(2)(dabco)(H2O)(0.5)(DMF)(4)), more commonly known as ZnDABCO. Equilibrium adsorption isotherms for four industrially relevant gases (CO2, CO, CH4 and N-2) were measured up to 26 bar at three different temperatures (294, 314 and 350 K) using a standard gravimetric method. The isotherms were modeled using modified virial equation. Ideal Adsorbed Solution Theory (IAST) was used to predict selectivity of binary mixtures. The results indicate that absence of open metal centers in the ZnDABCO framework, results in lower capacities and adsorption enthalpies when compared to MOFs like CuBTC and MIL-101. The small values of adsorption enthalpy and Henry constant should make it easier to regenerate the adsorbent. IAST predicts an increase in the selectivity of CO2 over the other three gases, with increasing pressure and CO2 mole-fraction; this phenomenon is attributed to the increase in lateral interactions between the adsorbed CO2 molecules. IAST predictions also indicate that this framework shows selectivity for CH4 over CO. (C) 2011 Elsevier B.V. All rights reserved.