Adsorption of CO2, CO, CH4 and N2 on DABCO based metal organic frameworks

In this work, we report the gas adsorption properties of Ni-2(bdc)(2)(dabco)(H2O)(0.5)(DMF)(4) and Cu-2(bdc)(2) (dabco)(H2O)(0.5)(DMF)(4), which are more commonly known as NiDABCO and CuDABCO, respectively. Equilibrium adsorption measurements on these materials have been performed for four industrially relevant gases (CO2, CO, CH4 and N-2), in the pressures range 0-25 bar and at three different temperatures (294, 314 and 350 K) using a standard gravimetric method. Virial and modified virial equations were used to model adsorption isotherms. Effect of adsorbate polarity and polarizability on adsorption characteristics of these MOFs is discussed. These compounds have similar adsorption characteristic as that of another DABCO based metal organic framework (MOF) viz. ZnDABCO. All DABCO compounds have saturated metal sites which result in small Henry's constants, low adsorption enthalpies at zero coverage and therefore require milder regeneration condition compared to MOFs with open metal sites like MgDOBDC, MIL-101, CuBTC, etc. IAST was used to predict CO2 selectivity over other gases as well as that of CH4 over CO. As in case of ZnDABCO, for both NiDABCO and CuDABCO the selectivity of CO2 increases with increase in pressure and CO2 mole-fraction. (C) 2012 Elsevier Inc. All rights reserved.