COSMO-descriptor based computer-aided ionic liquid design for separation processes. Part I: Modified group contribution methodology for predicting surface charge density profile of ionic liquids

- COSMO-GC-IL method is proposed to predict σ-profiles and cavity volumes of ionic liquids.
- Isomers of ionic liquids are completely distinguishable.
- COSMO descriptors are established and two parameters are utilized for modification.
- The method is validated by activity coefficients and LLE compositions.

When applying COSMO-based models in Computer-Aided Ionic Liquid Design (CAILD), the generation of surface charge density profiles (σ-profiles) and cavity volumes (VCOSMO) of ILs is particularly important but too computationally expensive with quantum chemical calculations. In this work, a modified group contribution methodology, the COSMO-GC-IL method, is proposed for quick prediction of IL σ-profiles and VCOSMO based on σ-profiles of IL groups in their reference states (COSMO descriptors), together with two modification parameters (stretch and translation parameters). The influence of molecular environment on target groups can be well described and IL isomers are thereby distinguishable. To verify the method, σ-profiles and VCOSMO generated from the present method and from the DMol3 database are employed to calculate activity coefficients of 28,644 binary systems and 3410 liquid-liquid equilibria of ternary mixtures. Their close results in most cases demonstrate the reliability of the COSMO-GC-IL method.