What is it about?

What happens to a liquid mixture when it is driven by pressure into an initially empty matrix? What if the matrix has an ordered pattern of molecular-sized pores? To answer this question, we injected an ethanol-water solution into one of such porous materials by using a diamond anvil cell. In this apparatus, the sample is compressed between the tips of two opposing diamonds and experiences huge pressures - about 10.000 times the normal atmospheric pressure. At these conditions, matter is subjected to forces which are comparable to internal atomic forces. New unexpected phenomena could show up. Now, let’s combine the use of high-pressures with the ordering effect of the empty pore matrix and see what happens to our mixture.

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Why is it important?

How it is difficult to separate alcohol-water mixtures into their components, it is certainly well known. This is a problem also for sustainable processes - such as the production of biofuels. Thanks to high pressure and to the porous matrix, here we observed the separation of ethanol and water, leading to a beautiful pattern of clusters. The clusters – rows of ethanol dimers, and square water tetramers - occupy different regions of the host matrix and alternate like tiles forming a nice molecular mosaic – a “two-dimensional architecture” – inside the porous host. What’s really exciting is that the ordered pattern, created by high pressure, also remained stable by bringing the material back to atmospheric pressure. This means that using high pressures and porous hosts, we can obtain new materials, which are stable at normal conditions, and could be exploited in applications.

Perspectives

Disclosing the way in which molecules and nanoparticles assemble at high pressure conditions, under the guidance of a matrix with molecular-sized pores, is among the next challenges. Another one is the actual production of technologically relevant materials through the combined use of pressures and suitable porous matrices. These goals could be achieved only through a close collaboration between experiment and theory. In a wider perspective, understanding the behavior of matter at high pressures is also of central relevance in science. Pressure effects are ubiquitous, in chemistry, physics, earth and planetary sciences, as well as in many industrial processes and technological applications. High-pressure conditions are also hypothesized to explain the origin of complex chemistry and life. The study of this exotic regime, so different from our everyday-life, may reveal plenty of interesting phenomena, which would be hard to imagine based on our experience only.

Gloria Tabacchi
university of insubria

Read the Original

This page is a summary of: Cover Picture: Irreversible Conversion of a Water-Ethanol Solution into an Organized Two-Dimensional Network of Alternating Supramolecular Units in a Hydrophobic Zeolite under Pressure (Angew. Chem. Int. Ed. 8/2017), Angewandte Chemie International Edition, January 2017, Wiley,
DOI: 10.1002/anie.201700219.
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