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PUBLICATION IN NATURE COM­MU­NI­CA­TIONS

Prof. Se­bas­ti­an Henke’s Group Develops Novel Responsive Materials

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Portrait of a man © Nikolas Golsch​/​TU Dortmund
Prof. Se­bas­ti­an Henke teaches and conducts research in the Department of Chemistry and Chemical Biology at TU Dortmund University.
A research team associated with Prof. Sebastian Henke’s group in the Department of Chemistry and Chemical Biology at TU Dortmund University, in cooperation with partners at Ruhr Universität Bochum, has investigated the extraordinarily responsive behavior of porous metal-organic framework compounds. These can, depending on conditions of their physical environment, crumple up like a piece of paper and unfold again. The findings, which are highly relevant for applications such as energy storage or molecular separation, were recently published in the renowned scientific journal Nature Communications.

Metal-organic frameworks, MOFs for short, are synthetic materials. Composed of organic and inorganic molecules, they have a porous, open structure. Some MOFs have responsive properties; that is, they change their crystal structure depending on conditions of their physical environment. Thus the size and shape of the pores can change, for example, if one varies the chemical composition of the ambient atmosphere or exerts mechanical pressure. Among other things, this responsiveness enables MOFs to store gases very efficiently or to separate molecules from one another.

Doctoral candidate Roman Pallach from Prof. Sebastian Henke’s group has now discovered a new form of responsiveness in MOFs: Through targeted chemical modification of the organic MOF building blocks, the networks of pores no longer switch back and forth between two ordered, crystalline states, but rather between an ordered state and one that is very complex and disordered. The modified building blocks generate competing interactions within the network structures, so that the disordered state is preferred when guest molecules – stored gases, for example – are absent in the pores.

Graphic of Metal-Organic Frameworks: Two networks (ordered and disordered) are juxtaposed. © Arbeitsgruppe Henke​/​TU Dortmund
If the organic MOF building blocks are chemically modified, the networks change to a disordered state.

“When we remove the guest molecules from the pores, the network is, in a sense, frustrated, and it can only fold up in a disordered manner,” says Prof. Sebastian Henke. “With these MOFs, folding up while maintaining the order is not possible.”