This work forms part of the doctoral thesis of Mónica Giménez Marqués, co-supervised by Guillermo Mínguez Espallargas and Eugenio Coronado –all of them members of the ICMol–, which was defended on November 14th. The authors have been able to modify a magnetic property, spin-crossover transition, through CO2 gas sorption, an unprecedented finding. This study has been published recently in Journal of the American Chemical Society and opens the possibility of using the material as a sensor capable of discriminating between CO2 and N2.

The spin-crossover phenomenon is observed in materials whose metal centres may exist in two electronically different states, high spin and low spin, and the transition between both states can be induced by an external stimulus, being temperature the most common. This bistability provides these materials with a great interest for their application as sensors or magnetic memories.

The authors of this study have shown that the transition temperature of a spin-crossover coordination polymer can be modulated through physisorption of CO2 gas molecules. These molecules interact weakly with metal-organic frameworks, thus causing no effects in other spin-crossover materials. However, the approach followed by the researchers at ICMol consists on the synthesis of a coordination polymer with discrete internal voids such that the CO2 molecules are confined in a more restricted space. This has permitted the observation for the first time of the tuning of a spin-crossover temperature through gas sorption.