Adsorption of several gases on flexible metal organic framework [Cu(dhbc)2(4,4′-bpy)]•H2O

The adsorption of ten gases on the flexible metal organic framework material [Cu(dhbc)(2)(4,4'-bpy)]center dot H2O (Cu(db)) has been measured over a wide range of temperatures and pressures. The gate opening condition and driving force behind gate adsorption for Cu(db) were discussed by examining the adsorption isotherms. The adsorption isotherms for each adsorbate can be generalized to a characteristic curve using the adsorption potential energy (epsilon) and the adsorption volume. The adsorption potential (epsilon(gate)) at gate opening is almost constant over a wide range of temperatures; thus, the gate pressure at a desired temperature can be deduced using the epsilon(gate) evaluated from one adsorption isotherm. The gate opening capacity of the gases was arranged in the order: CO2 = N2O > C2H4 = Xe > CH4 > CO > O-2 > Ar = N-2 > H-2, which is governed by the interaction energy between the outer surface of Cu(db) and the adsorbate. It is suggested that the gate effect is brought about when the integral interaction energy of adsorbates with the Cu(db) surface exceeds a defined limit correlating with the pi-pi stacking energy of Cu(db) layers. (C) 2011 Elsevier Inc. All rights reserved.