The effect of ionic liquid compounds on the exfoliation of the two-dimensional layer of molybdenum disulfide

Ionic liquids (ILq) have attracted large interest among researchers due to their green nature and lower costs compared to organic solvents. Herein, we theoretically investigated the effects of changing the cationic and anionic combination of the ILqs to exfoliation of two-dimensional layer of molybdenum disulfide (MoS2). Density functional theory (DFT) and the Atoms in Molecules (AIM) analysis were performed for calculation of interaction energies and nature of interactions of ILqs with MoS2 nanosheet. Based on our results, we suggest that the intermolecular associations in the form of molecular networks in the various ILq compounds may be crucial to the solvent's intercalation and exfoliation ability. Our calculations reveal that among the nine examined ILq compounds, the highest clustering ability belongs to [Bpy][X] pairs ([X] = BF4, PF6, and Tf2N). Our results also show that the [Bpy][X] were the most efficient compounds for exfoliation of MoS2 nanosheet. As the solvent clustering increases, diffusion into the galleries of the bulk MoS2 becomes more efficient and exfoliation efficiency increases appreciably. Moreover, the calculated binding energies showed that the clustering between [Bpy][X] pairs decreased by increasing the anion size. The results found in the present study provide a framework for rational manipulation of the compositions of the ILqs for the exfoliation of the two-dimensional materials.