Liquids have nice properties, like the capability of "filling" cavities, moving around very easily. Solids, on the other hand, can be impermeable or can be porous, like sponges.
Combining the properties of both seems a contradiction: a liquid will fill any cavity, hence nothing will be left "unoccupied", available to absorb other substances. True, a liquid, like water, can absorb gases, like oxygen or CO2. But what happens is that the gaseous substance gets dissolved in the liquid but only a small fraction can be dissolved. On the other hand a solid, like a sponge, can have plenty of cavities that can be filled in, hence a much higher percentage of a gaseous (or liquid) substance can be captured.
Well, it looks like scientists at the Queen's University in Belfast have managed to create a porous liquid, a liquid sponge, by designing molecules that behave like a liquid but that are shaped like doughnuts, with a cavity that can be used as a cistern (see the image).
What I found really interesting is that they really designed the shape of the molecules, something that would have been unconceivable only ten years ago. The cavity within the molecules is 500 times greater than in normal molecules forming a liquid, and still the whole is a liquid. This means that this liquid can adsorb 8 times the amount of methane gas a normal liquid would do.
This porous liquid can have several applications including adsorption of CO2.