Designing and Understanding Microporosity in Liquids

Standard microporous materials are crystalline solids that exhibit a regular array of cavities of uniform size and shape. Packing and directional bonding between molecular building blocks give rise to interstitial pores that confer catalytic and sorption properties to the material. In the liquid state interstitial cavities are transient, however permanent and intrinsic 'pores' can potentially be built into the structure of the constituent molecules. With the aid of computer simulations we have designed, produced and characterised a series of liquids made of hollow cage-like molecules, which are decorated with hydrocarbon chains to make them liquid at accessible temperatures. Experiments and simulations demonstrate that chain length and size of terminal chain substituents can be used to tune, within certain margins, the availability of intramolecular cavities in such neat liquids. Simulations identify a candidate "porous liquid" in which 30% of the hollow cages remain empty in the liquid state. We will also show that small guest molecules can selectively occupy these empty cavities.