CO2 adsorption, selectivity and water tolerance of pillared-layer metal organic frameworks

The potential for two water tolerant three-dimensional pillared-layer metal organic frameworks (MOFs) M2(BDC)2(Dabco) (M = Zn, Ni) to selectively adsorb and separate CO2 is considered. Isotherms for CO2, CH4 and N2 were measured from 0 to 15 bar and for O2 from 0 to 2.5 bar at temperatures between 25 and 105 °C. The isotherms give CO2 adsorption capacities of 13.7 and 12.5 mol/kg for Zn2(BDC)2(Dabco) and Ni2(BDC)2(Dabco) at 25 °C and 15 bar, respectively. Both materials have higher CO2/N2 selectivity than CO2/CH4 selectivity and low heats of adsorption. The structures of the two MOFs are stable after O2 and 30% relative humidity water vapor sorption at 25 °C, but collapsed after 60% relative humidity water vapor sorption at 25 °C.