A molecular dynamic insight into CO2 diffusion of type III porous liquids

As emerging materials, porous liquids have shown good performance in gas separations attributed to porosity and fluidity. In the present work, a microscopic insight into CO2 diffusion of type III porous liquids was revealed by molecular dynamic simulation. First, A model of [EMIm][NTf2]/ZIF-8 type Ⅲ porous liquids was constructed. The internal permanent, rigid, vacant pores in the porous liquids were demonstrated by molecular dynamics simulation. It was found these pores were still kept after 12 ns dynamic simulation, and the calculated specific surface area and the pore volume of the porous liquids were 0.139 cm3/g and 939 m2/g, respectively. Then the models of CO2-type Ⅲ porous liquids were constructed to study the diffusion behavior of CO2 molecules in porous liquids. It was found that ZIF-8 dominated the CO2 absorption by analyzing CO2 relative concentration. Subsequently, the effect of different parameters, including temperature, pressure, and CO2 loading on CO2 diffusion in porous liquids was studied. The results showed CO2 diffusion ability in the porous liquid enhanced with increasing temperature, and CO2 loading. and it was insensitive to pressure. Finally, the interaction energy was calculated, and the interaction energy between CO2 and [EMIm][NTf2], ZIF-8 followed the order CO2-ILs < CO2-ZIF-8. The research approach in this paper assists in obtaining the micro-informations of porous liquids.