(466c) Correlation-Based Predictions of Gas Solute Diffusivity in Viscous Ionic Liquid Solvents: Logarithmic Diffusivity Relationships with Solvent-Accessible Surface Area

In our prior study [J. Phys. Chem. B 127, 9144–9154 (2023)], we introduced a new scaling relationship to predict gas solute diffusion at challenging conditions, focusing on CO₂ and SO₂ diffusion in multivalent ionic liquid solvents. This work extends our initial exploratory study into a much broader array of systems, encompassing additional solutes (N₂, CH₄, C₂H₆, C₃H₈, C₃H₈O, and H₂O) and a variety of different ionic liquid species ([Bzmim₃]³⁺, [Bzmim₄]⁴⁺, [BMIM]⁺, [EMIM]⁺, [HMIM]⁺, [NpO₂]^2−, [BzO₃]^3−, [BF₄]^-, [Tf₂N]^-, and [PF₆]^-). Our study demonstrates a remarkably robust logarithmic correlation between solute diffusion and solvent-accessible surface area across twenty different additional systems. We perform comprehensive analyses of the underlying molecular phenomena responsible for this correlation, including pocket lifetime distributions, void space dynamics, and Voronoi tessellation, in order to elucidate a stronger mechanistic understanding of this behavior. Our findings highlight the link between the solute hopping behavior and the size and shape of the void network, revealing that diffusion is characterized by an ensemble of large spherical cavities connected via tube-shaped channels. Overall, our scaling approach provides an extremely efficient approach for predict diffusion from analyses of short simulations at higher temperatures.