Grand canonical Monte Carlo simulations were conducted to systematically evaluate the adsorption separation of three binary mixtures, CO2/CO, C2H4/CO2, and C2H4/C2H6, in a metal-organic framework Cu-BTC at room temperature. The simulated results showed that Cu-BTC could be potentially used for the purification of carbon monoxide, capture of carbon dioxide and separation of olefin/paraffin. The topology structure of the side pockets in Cu-BTC caused the selective adsorption behaviors between gas components, and its effects were more evident at low adsorption loadings. The results also provided qualitative guidelines for the synthesis and design of new MOFs for applications in mixture separations. (c) 2007 Elsevier B.V. All rights reserved.