Modular Type III Porous Liquids Based on Porous Organic Cage Microparticles

Abstract

The dispersion of particulate porous solids in size-excluded liquids has emerged as a method to create Type III porous liquids, mostly using insoluble microporous materials such as metal-organic frameworks and zeolites. Here, the first examples of Type III porous liquids based on porous organic cages (POCs) are presented. By exploiting the solution processability of the POCs, racemic and quasiracemic cage microparticles are formed by chiral recognition. Dispersion of these porous microparticles in a range of size-excluded liquids, including oils and ionic liquids, forms stable POC-based Type III porous liquids. The flexible pairing between the solid POC particles and a carrier liquid allows the formation of a range of compositions, pore sizes, and other physicochemical properties to suit different applications and operating conditions. For example, it is shown that porous liquids with relatively low viscosities or high thermal stability can be produced. A 12.5 wt% Type III porous liquid comprising racemic POC microparticles and an ionic liquid, [BPy][NTf 2 ], shows a CO 2 working capacity (104.30 µmol g L −1) that is significantly higher than the neat ionic liquid (37.27 µmol g L −1) between 25 and 100 °C. This liquid is colloidally stable and can be recycled at least ten times without loss of CO 2 capacity.

Shining a Light on Photoresponsive Type III Porous Liquids

“…To date, a wide variety of liquids have been used, including organic solvents, oils, and ionic liquids. 37,38 For this study, we screened a small number of liquids that have previously been reported as being size-excluded for POCs and MOFs, including silicone oil AR 20, and the ionic liquids ). Ionic liquids are good candidates for porous liquids due to their low vapour pressures, compatibility with organic and inorganic materials,…”

“…As for porous solids, the most common gas release mechanisms are pressure and temperature swings. 11,29,30 This significantly limits the solvent choice in a porous liquid, restricting us to solvents that have a low or (ideally) near-zero vapour pressure. 11,31 There is also a significant parasitic energy penalty with pressure and temperature swings.…”

Shining a Light on Photoresponsive Type III Porous Liquids

“…To date, a wide variety of liquids have been used, including organic solvents, oils, and ionic liquids. 37,38 For this study, we screened a small number of liquids that have previously been reported as being size-excluded for POCs and MOFs, including silicone oil AR 20, and the ionic liquids ). Ionic liquids are good candidates for porous liquids due to their low vapour pressures, compatibility with organic and inorganic materials, and their ability to be tailored to suit different applications.…”

Porous liquids – the future is looking emptier

“… 49 While most of these systems relied on the use of a MOF, ZIF, or zeolite, as the porous material, more recently there have been examples of alternative pore carriers being used to form type III porous liquids, including the dispersion of HS nanospheres in dimethylaminoethoxyethanol, 50 hollow carbon nanospheres in polymeric ionic liquids, 51 and POC microparticles in a range of oils and ionic liquids. 52 …”