The crystal structure of copper squarate, a wonder with many applications

Scientists have determined the crystal structure of copper squarate, a metal-organic material.

These researchers have discovered that, as occurs in other materials of this type, the crystalline structure of copper squarate contains large empty channels that give it great porosity and, together with its structural uniformity, make it possible to use, for example, in the absorption of polluting gases and chemical compounds.

“By knowing the structure of copper squarate, we have been able to study its compressibility and see that the material has negative linear compressibility (NLC), a property that has multiple potential applications since materials of this type, strange as it may seem, are compressed when they are stretched and they expand when pressed”, explains Vicente Timón, co-author of the study and researcher at the Institute for the Structure of Matter (IEM), dependent on the Higher Council for Scientific Research (CSIC), in Spain.

The authors of the study have reached these conclusions through theoretical computational methods.

Possible uses for materials with negative linear compressibility include the development of ultrasensitive pressure sensing devices, optical telecommunication devices, artificial muscles, body armor, and devices for sound attenuation, superconductivity modulation, ferroelectric enhancement, and stabilization of signal transmission.

Three-dimensional image of a channel in the crystal structure of copper squarate. (Image: CSIC)

“Due to the multitude of applications of these materials, a large amount of resources has been devoted to their research. But although the search for new materials has been intense and fruitful, research is still in its infancy. For this reason, being able to determine the crystalline structure of copper squarate is an important advance in this field”, points out Francisco Colmenero, first author of the study and scientist at the Complutense University of Madrid (UCM) in Spain.

The results of the study suggest a simple way to find new materials with negative linear compressibility that have a simple chemical composition and high availability, by searching for empty channels between compounds with known crystal structures. The results also point to a method to obtain new materials with negative linear compressibility artificially by generating structures with empty structural channels. “Given that nanotechnology promises the construction of materials with almost any geometry, the artificial reproduction of the structural characteristics that lead to the effect of negative linear compressibility should allow the generation of a wide range of metamaterials with desirable mechanical properties”, adds the researcher of the CSIC.

The study is titled “Compressing the Channels in the Crystal Structure of Copper Square Metal-Organic Framework.” And it has been published in the academic journal Solids. (Source: María González / Alda Ólafsson / CSIC)