Clip-off Chemistry: a powerful novel strategy for synthesising new materials

by Virginia Greco

A paper recently published in the prestigious journal “Angewandte Chemie” proposes a novel approach to the synthesis of molecular structures that can allow material scientists to design and build a set of new materials. By splitting in a controlled way only selected bonds in the lattice of some molecules or materials, structures exhibiting different properties from the original ones are obtained. This work was coordinated by ICN2 group leader Prof. Daniel Maspoch and ICN2 senior researcher Dr Inhar Imaz.

In the quest for new materials with excellent properties for specific applications, scientists have developed various synthesis strategies over the years, which have given them increasingly precise control over the process and, consequently, over its outcome. In reticular chemistry, specifically designed molecular building blocks are used to create new porous crystal structures, whose properties are strongly related to the periodic arrangement of those basic components. These so-called reticular materials include metal-organic frameworks (MOFs), covalent-organic frameworks (COFs) and metal-organic polyhedra (MOPs).

A team of researchers from the Catalan Institute on Nanoscience and Nanotechnology (ICN2), the Materials Science Institute of Madrid (ICMM-CSIC), the Universitat Autònoma de Barcelona (UAB) and the ALBA Synchrotron Light Facility (Barcelona) —coordinated by Prof. Daniel Maspoch and Dr. Inhar Imaz, respectively group leader and senior researcher in the ICN2 Supramolecular NanoChemistry and Materials Group— has pushed forward the approach to structure design of reticular chemistry by proposing a novel synthetic strategy. In what they named Clip-Off Chemistry, new materials or molecules are generated by selectively breaking some of the bonds in known reticular materials.

In a paper recently published in Angewandte Chemie, they demonstrated the validity of their approach by modifying three-dimensional MOFs or zero-dimensional MOPs via splitting – rather than formation— of bonds in their architecture. Since only selected bonds are cleaved, the resulting structures present a new topology and different properties, while retaining its original dimensionality. For this technique to work, however, the precursor reticular material must have cleavable alkene groups (which are functional groups containing one or more carbon-carbon double bonds) located at specific positions in its structure.

Using Clip-off Chemistry for the first time, the authors of this work synthesised new molecular structures, starting from existing ones. In order to perform these syntheses, cleavable alkene groups were chemically introduced in the precursor materials. In practice, some of the original linkers were replaced with others of similar size and geometry containing the desired groups, that is, the breakable bonds. After appropriate treatment, those bonds split and what is left is a lattice structure made up only of the circuits of connections that did not include the cleavable groups.

A powerful new tool for forging novel materials and molecules is therefore provided to scientists. The application of such technique to a variety of structures can lead to the engineering of a plethora of new molecular blocks and structures.

This research was carried out in the framework of the CLIPOFF-CHEM project, which has received funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme (grant agreement No. 101019003).

Reference article:

Yunhui Yang, Anna Broto-Ribas, Borja Ortín-Rubio, Inhar Imaz, Felipe Gándara, Arnau Carné-Sánchez, Vincent Guillerm, Sergio Jurado, Félix Busqué, Judith Juanhuix, Daniel Maspoch, Clip-off Chemistry: Synthesis by Programmed Disassembly of Reticular Materials. Angewandte Chemie, November 2021. DOI: 10.1002/anie.202111228