Unlocking CO2 separation performance of ionic liquid/CuBTC composites: Combining experiments with molecular simulations

In this work, we propose a computational methodology based on the state-of-the-art molecular simulations of IL/CuBTC composites composed of ILs having the same cation, 1-n-butyl-3-methylimidazolium ([BMIM]+), and various anions. Using grand canonical Monte Carlo (GCMC) simulations, we predicted CO2, CH4, and N2 uptakes of seven different IL/CuBTC composites and compared the simulation results with our experimental gas uptake measurements to select the most appropriate force field that best represents the experimental results. Motivated from the good agreement between experiments and simulations, we applied the same method to estimate the gas adsorption in two new IL/CuBTC composites which have been synthesized and characterized for the first time in this work. Molecular simulations accurately predicted the experimental gas uptakes of newly synthesized IL/CuBTC composites, validating the transferability of our approach to different types of IL-incorporated CuBTC samples. We also provided a detailed analysis of binary gas mixture separation performances of IL/CuBTC composites and self-diffusion coefficients of gases in the composites performing GCMC and molecular dynamics simulations, respectively. Results showed that IL/CuBTC composites have higher CO2/CH4, CO2/N2, and CH4/N2 selectivities than those of CuBTC, demonstrating a broad potential of these composites for CO2 separation from natural gas and flue gas mixtures. The combination of experiments and molecular simulations that we described in this study will be useful to efficiently screen various IL/MOF composites to unlock their full potential for gas separation applications.