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

Abstract

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.