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.
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.
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.
You can read the full text:
spontaneous formation of water square tetramers
YouTube video showing the first steps of the organization process inside the porous host: initially disordered water molecules form water tetramers
Molecular funky dance in confined spaces
YouTube video highlighting the stability of the water and ethanol clusters: the molecules happily dance to the funky music, but the supramolecular units remain stable!
A more extended version of this explanation (with embedded movies) is reported in my blog
From chaos to order: Artistic vision of the pressure-driven metamorphosis of a disordered ensemble of molecules (the water-ethanol liquid mixture) into an ordered pattern of clusters inside the porous matrix
Supporting data: experimental and computational procedures, further data, and calculated coordinates of the optimized structures.
High pressure and small spaces create order from disorder
Our work has been covered by MRS Bulletin with this excellent news article by Tim Palucka
Green open access
Green Open Access version of this communication (author's accepted manuscript).
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