Metal organic frameworks (MOFs) materials have received extensive attention in capture and separation of CO₂. Herein, molecular dynamic simulation (MD) and grand canonical Monte Carlo (GCMC) simulation were used to investigate the process of negative gas adsorption to DUT-49, an MOF, and the effect of structural transition on the CO₂/N₂ adsorption and separation behavior. Results showed that DUT-49 underwent stable structural deformation at 20-60 MPa, with a transition between open pore (DUT-49-op) and closed pore (DUT-49-cp). Its adsorption capacity decreased with the increase of temperature. DUT-49-cp owned a contractive framework, exhibiting a considerably decreasing adsorption capacity due to reduction of effective adsorption sites. In addition, its selectivity decreased significantly compared with that of DUT-49-op, and decreased with increase of temperature, which is not conducive to gas separation. The present study provides a scientific basis for the development of adsorbent materials.