ePC-SAFT-DFT is a powerful tool for studying the properties of confined ionic liquids for CO2 separation, in which efficient algorithms are required to obtain the calculation efficiently. In this work, the feasibility of accelerating the ePC-SAFT-DFT calculation with the Chebyshev pseudo-spectral collocation method was discussed for the confined ionic liquid (IL)–CO2 systems. In addition, a general scheme was proposed to search the electrical boundary potential. The new algorithm was further combined with the general scheme to model the confined IL–CO2 systems. It was found that the Chebyshev pseudo-spectral collocation method can improve the efficiency of the ePC-SAFT-DFT calculation significantly. Moreover, the new algorithm can be further combined with the general scheme to efficiently describe the density profile of the IL–CO2 system inside the electroneutral nanopores.