Determining Porosity of Type II Porous Liquids through Partial Molar Volumes.

Porous liquids are liquids with intrinsic microporosity that have the potential to revolutionize gas separation processes. The concept of porous liquids was proposed by James et al. in 2007. There are three types of porous liquids: Type I microporous solids that retain their porosity when raised to temperatures above their melting point, Type II rigid, microporous host molecules dissolved in a solvent that is too large to enter the pores and creates a porous solution, and Type III microporous frameworks dispersed in a solvent that is too large to enter the pores. This study focuses on Type II porous liquids since they are stable solutions formed by dissolving porous organic cages (POCs) in sterically hindered solvents, which may be more applicable to large-scale separations. Currently, the porosity of porous liquids is determined via time-consuming gas evolution experiments or by collecting gas sorption isotherms. A facile and quick method for determining if a candidate liquid is porous will accelerate the discovery and impact that porous liquids have for relevant applications. In this work, the partial molar volume of porous organic cages dissolved in a variety of solvents is experimentally obtained from the solution density. The partial molar volume is defined as the rate of change of the total volume of solution with the change in the amount of the solute component. Consequently, when a POC is added to a e hypothesized that the solution volume of the overall system remains constant, and the partial molar volume of the cage will be small since the solvent molecules can fill the pores of the POC. In contrast, the partial molar volume of the cage should increase when POC is added to a larger solvent. This poster describes a method where the partial molar volume of POCs dissolved in large and small solvents can be measured via facile density measurements. Through this study, we show that partial molar volume experiments could quickly determine if a candidate liquid is porous.