19.02.2020 change 19.02.2020
Ludwika Tomala
Ludwika Tomala

Liquid Filter? Time for Porous Liquids

Source: Nature Chemistry Source: Nature Chemistry

A team of scientists from the Adam Mickiewicz University in Poznań developed a liquid filter: a porous liquid capable of capturing specific substances from mixtures. Researchers hope that thanks to this invention, effective purification of mixtures can become much simpler.

We have contact with porous materials every day. They include sponges, pumice stones, carbon filters for water and air purification. These materials contain pores - small spaces, in which other substances can be bound, for example impurities.

Porous materials - usually in the form of solids - are used in industry, for example to separate a mixture of different chemicals or purify gases.

However, for some time now scientists have been working on porous liquids. They hope that such liquid substances will even more effectively separate some ingredients of mixtures from others.

Perhaps in some cases it will be more convenient and safer to pass the filtered material through a tank filled with a porous liquid than through a conventional, solid state filter. Scientists also hope that porous liquid will be much easier to reuse. In order to release bound particles from such a porous liquid, it is enough to simply evaporate it.

Now an international team of scientists (publication under the supervision of Professor Jonathan Nitschke from Cambridge appeared in Nature Chemistry https://www.nature.com/articles/s41557-020-0419-2) designed and produced a porous ionic liquid.

Its pores are nanometer-sized, have a tetrahedron shape and exhibit high selectivity in binding not only structurally different substances in the liquid state (e.g. alcohol isomers), but also gases (e.g. fluorohydrocarbons, i.e. Freon).

One of the authors of the publication, Dr. Artur Stefankiewicz, a professor at the Faculty of Chemistry and the Centre of Advanced Technologies, Adam Mickiewicz University, explains that the ability to separate fluorohydrocarbons is important because the compounds of this group are largely responsible for the ozone hole phenomenon.

HOW DOES IT WORK?

`Due to the fact that the obtained liquid material has hollow and evenly spaced nanopores of a strictly defined size, we can extremely selectively capture a chemical compound, for example a gas molecule, whose shape and size fit the space in these pores`, the chemist says.

These invisible recesses can even separate structurally similar compounds. They will allow to separate particles with similar or even the same chemical composition, but different shapes.

Researchers expect that the methodology described in the paper, will also allow to easily adapt the produced porous material to bind a specific type of particles. These pores are well-known coordination complexes made of organic molecules and metal ions.

According to Stefankiewicz, it will be possible to design the size and shape of liquid pores to match, for example, the selected catalyst molecule. `Catalysts used in industry to run chemical processes are usually expensive. The goal is to use them in the smallest possible amounts, and reuse them if possible. Porous liquids could potentially be used to capture catalyst particles from the reaction mixture`, the chemist explains.

In the research project presented in Nature Chemistry, Dr. Artur Stefankiewicz and PhD student Anna Walczak were responsible for the synthesis of organic components that make up the porous liquid complex.

`Such structures are a very interesting alternative to porous materials in solid form`, the scientist concludes.

PAP - Science in Poland, Ludwika Tomala

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