Supplementary Material

The supplementary material provides Tables S1-S6: details of the MD simulations performed for all CO2-IL mixtures; Table S7: calculated molar volumes of the species; Table S8: coordination numbers for the cation-anion interaction in homologous series of ionic liquids as a function of mole fraction of CO2; Table S9: electronic energies, absolute chemical hardness, Mulliken electronegativity, vertical ionization potential and vertical electron affinity VEA of the species, calculated by DFT; Table S10: empty volumes of the different systems studied; Table S11: percentage increase in the number of empty voids in [C2C1im]+- and [C6C1im]+-based ionic liquids as a function of CO2 mole fraction; Figs. S1-S2: pair radial distribution functions for some interacting centers in the polar moiety of selected ionic liquids; Figs. S3-S4; radial distributions between CO2 and the carbon atoms of the imidazolium ring for ILs based on [C2C1im]+ cations; Figs. S5-S10: combined radial and angular distribution functions for the N3cation-Anion distance and N1cation-N3cation-Anion angle for [C2C1im]-based IL mixtures with CO2; Fig. S11: spatial distribution functions of anions around [C2C1im]+ as a function of CO2; Figs S12-S18: pair radial distribution functions between the center-of-mass of CO2 and selected interactions centers in the anion and the cation for the studied ILs; Fig. S19: Snapshots of simulation boxes highlighting the CO2 neighboring; Fig. S20: probability distribution function of aggregates of the imidazolium cation ring alkyl chains; Fig S21: average number of neighbors for CO2 aggregates in the ILs; Figs. S22-25: interaction energy decomposition analysis for all IL-CO2 mixtures; Figs. S26-S27: void distribution analyses for selected IL-CO2 mixtures; Figs. S28-S29:void interstitial network analyses for selected IL-CO2 mixtures.