Integrating Molecular Simulations with Machine Learning Guides in the Design and Synthesis of [BMIM][BF 4 ]/MOF Composites for CO 2 /N 2 Separation.

Considering the existence of a large number and variety of metal-organic frameworks (MOFs) and ionic liquids (ILs), assessing the gas separation potential of all possible IL/MOF composites by purely experimental methods is not practical. In this work, we combined molecular simulations and machine learning (ML) algorithms to computationally design an IL/MOF composite. Molecular simulations were first performed to screen approximately 1000 different composites of 1- n -butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF 4 ]) with a large variety of MOFs for CO 2 and N 2 adsorption. The results of simulations were used to develop ML models that can accurately predict the adsorption and separation performances of [BMIM][BF 4 ]/MOF composites. The most important features that affect the CO 2 /N 2 selectivity of composites were extracted from ML and utilized to computationally generate an IL/MOF composite, [BMIM][BF 4 ]/UiO-66, which was not present in the original material data set. This composite was finally synthesized, characterized, and tested for CO 2 /N 2 separation. Experimentally measured CO 2 /N 2 selectivity of the [BMIM][BF 4 ]/UiO-66 composite matched well with the selectivity predicted by the ML model, and it was found to be comparable, if not higher than that of all previously synthesized [BMIM][BF 4 ]/MOF composites reported in the literature. Our proposed approach of combining molecular simulations with ML models will be highly useful to accurately predict the CO 2 /N 2 separation performances of any [BMIM][BF 4 ]/MOF composite within seconds compared to the extensive time and effort requirements of purely experimental methods.