In this work, a computational study is performed to evaluate the adsorption-based separation of CO2 from flue gas (mixtures of CO2 and N-2) and natural gas (mixtures of CO2 and CH4) using microporous metal organic framework Cu-TDPAT as a sorbent material. The results show that electrostatic interactions can greatly enhance the separation efficiency of this MOF for gas mixtures of different components. Furthermore, the study also suggests that Cu-TDPAT is a promising material for the separation of CO2 from N-2 and CH4, and its macroscopic separation behavior can be elucidated on a molecular level to give insight into the underlying mechanisms. On the basis of the single-component CO2, N-2 and CH4 isotherms, binary mixture adsorption (CO2/N-2 and CO2/CH4) and ternary mixture adsorption (CO2/N-2/CH4) were predicted using the ideal adsorbed solution theory (LAST). The effect of H2O vapor on the CO2 adsorption selectivity and capacity was also examined. The applicability of IAST to this system was validated by performing GCMC simulations for both single-component and mixture adsorption processes.