The material breathes in and out on command by means of a switch. Interestingly, the porous framework breathes by capturing and releasing carbon dioxide only when it receives a luminous stimulus at a specific wavelength. It is designed thanks to the collaboration of the research teams led by the Nobel Prize winner Ben Feringa, and by Prof. Sander Wezenberg of the University of Groningen and by Prof. Angiolina Comotti, full professor of Industrial Chemistry of the Department of Materials Science of the University of Milan – Bicocca. The research results “Modulation of porosity in a solid material enabled by bulk photoisomerization of an overcrowded alkene” (doi:10.1038/s41557-020-0493-5) have been recently published in the journal Nature Chemistry .
Common materials have multiple properties and functions which generally can vary with temperature or pressure. The real challenge for researchers is to design materials that are able to respond to a stimulus and perform an action by inserting a switch on the nanometer scale sensitive to a specific command. The molecular switch is a molecule that can receives a stimulus or a command and activates a function.
Inspired by biological systems capable of developing dynamic processes, in recent years numerous research groups have developed several machines and artificial molecular switches in solution capable of performing certain functions. The isotropic thermal motion, however, precludes any form of collective action and macroscopic work. On the contrary, the organization of solid-state machines and molecular switches are able to transform nanoscopic changes stimulated by light or heat into work of practical utility. Therefore, the current challenge is to organize machines and molecular switches that can perform selected and non-randomized rotary or switching motions.
The challenge was collected and won by the research groups of the University of Groningen and the University of Milan - Bicocca who have exploited materials with high porosity thanks to which they can incorporate molecular switches, providing the free volume essential for dynamic motions. The material behaves as an armor for flexible molecular components: the light and porous scaffold does not prevent the motion of the molecular switch which is controlled by light / heat. CO2 capture is therefore modulated by light and / or heat due to the quantitative photoisomerization of the molecular switch.
These new prototype materials lead to the generation of macroscopic properties such as the regulation of the quantity of absorbed CO2 controlled by external stimuli. This discovery also opens up new opportunities in the field of chiral molecule separation technologies in the presence of a molecular switch that modulates the pore size.
The importance of this research is also highlighted by the journal Nature Chemistry itself by dedicating a section of the News & Views section entitled "Photoswitching to the core".