Tuesday , June 15 2021

Materials that open at the height of the moment

(Nanowerk NewsResearchers from the Kyoto University have designed copper-based material to control the temperature for sifting or storing different types of gases (science, "Design and control of the process of gas diffusion in nanoporous soft crystal").

The rationale used in designing the material described in the journal Science may serve as a plan to develop nanoporous materials with a wide variety of energy, medical and environmental applications.

The butterfly ligand is the key to creating a material that can selectively absorb and store various gas molecules
The butterfly ligand is the key to creating a material that can selectively absorb and store various gas molecules. (Image: Mindy Takamiya)

Porous nanomaterials that are currently used for gas separation and storage can not be adjusted: their pores are rigid and rigid. Susumu Kitagawa, Nobuhiko Hosono and their colleagues at the Kyoto University's Institute of Intelligent Cell Research (iCeMS) wanted to find a way to dynamically modify pore size in this type of material.

They designed a porous co-ordination polymer that was formed from copper atoms attached to butterfly ligands made of isophthalic acid and phenothiazine-5,5-dioxide. The resulting material consists of small nanocamera, each with eight convex channels. At very low temperatures the channels connecting the nanocabs were so narrow that they were effectively closed. As the temperature rises, the channels open more and more, allowing the gas molecules to move between the cells.

The team found that gas can move or lock in the material depending on the size of the gas molecules and how wide the material passages are at a given temperature. They also found that the material adsorbs gas at high temperatures and keeps it at ambient temperature by effectively storing the gas.

In addition, when researchers have applied gas mixtures to the material, they have found that they can emit gases based on the applied temperature. For example, the material selectively adsorbs oxygen when a gaseous mixture with equal concentrations of oxygen and argon is applied for one hour at -93 ° C and one bar pressure. The material selectively adsorbs oxygen even when the concentration of argon in the mixture is significantly higher than that of oxygen.

"The porous system that uses a robust thermally-active molecular functionality framework achieves temperature-controlled adsorption / desorption of gas by design, where local aperture flexibility plays a key role," the researchers conclude.

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