Quantum mechanics/molecular mechanics (QM/MM) molecular dynamics simulations have been carried out to model the scattering of hyperthermal (15 kcal/mol) CO2 on the surfaces of two common imidazolium based room-temperature ionic liquids (RTILs) [bmim][BF4] and [bmim][Tf2N]. Good agreement was achieved in comparison with experiment. The [bmim][BF4] surface is found to be more absorptive of CO2 than [bmim][Tf2N], which leads to greater loss in translational energy and less rotational excitation of CO 2's that scatter from [bmim][BF4]. These differences are found to result from a interplay of differences in the structure of the interface and the strength of interactions that depend on anion identity. Our results also suggest that CO2 interacts strongly with ionic species on the RTIL surfaces due to the large induced dipole moments on CO2 during the collisions. The inclusion of electronic polarization is critical in determining the final rotational excitation of CO2 compared to results from an MM model with fixed charge.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Surfaces, Coatings and Films
- Materials Chemistry