Nonadditive CO₂ Uptake of Type II Porous Liquids Based on Imine Cages

Type II porous liquids can potentially exploit the fluidity of liquids and sorption properties of porous sorbents, yet CO₂ uptake in porous liquids is still poorly understood. Molecular simulations and experiments are used to examine CO₂ uptake by a prototypical porous liquid composed of porous organic cages (CC13) in 2'-hydroxyacetophenone (2'-HAP). The simulations are in reasonable agreement with experimental measurements of CO₂ solubility and provide unambiguous information on the partitioning of CO₂ within microenvironments in the liquid. Analysis of CO₂ dynamics is performed using these simulations, including assessing the self-diffusivity of CO₂ in both the neat solvent and porous liquid. This offers insights into the kinetics of CO₂ uptake and transport in type II porous liquids based on imine cages. Experiments with type II porous liquids formed by dissolving CC13 in three different size-excluded solvents show nonadditive CO₂ absorption relative to predictions based on ideal volume additivity. This nonadditive absorption behavior is also observed in simulations. Nonadditive CO₂ uptake is also demonstrated in type II porous liquids based on another imine-based porous cage, CC19.