Structural and Dynamic Properties of CO ₂ in the Room-Temperature Ionic Liquid Hmim ⁺ TCΜ ^– as a Function of Pressure and Concentration: A Combined Experimental and Molecular Dynamics Simulation Study

The behavior of CO2 in [Hmim+][TCM–] was studied by using Gravimetric Absorption and Molecular Dynamics, with properties recorded up to 2 MPa. Among others, we focused on the previously unexplored structure and dynamics of the system. Results are discussed regarding the characteristics of the solution’s components, their mutual interactions, and the structure around CO2. Analysis revealed complex network-like microstructures formed by ions with cages hosting CO2, whose formation depends on intermediate and greater pressure. CO2 preferentially resides near the C01 site of the imidazolium cation ring, while locations at the COT cation tail end or outer TCM– sites are less favored. We found experimentally and through simulations that the diffusivity of CO2 increases with pressure, primarily due to local structural changes around the CO2. Also, these effects are evident in the behavior of the predicted relevant translational, reorientational, and van Hove self-part correlation functions.