A new family of porous metal-organic frameworks (MOFs) with flexible ligands has been created by UK scientists. 

MOFs consist of metal atoms linked by organic ligands. Their porous structure allows them to capture and store gases such as hydrogen and carbon dioxide. 

Rigid ligands are commonly used in MOFs, but Lee Brammer of the University of Sheffield, UK, and colleagues at the Universities of Liverpool and Strathclyde and the Daresbury Laboratory, UK, used flexible tetracarboxylate ligands and zinc to create their MOFs. Unusually, their material rearranged itself when carbon dioxide was removed or replaced.

'The field of MOFs has tremendous potential to deliver applications in a wide range of areas, for example molecular storage, sensing, separation science and catalysis,' Brammer said, 'Our hope was that our strategy may prove particularly useful for gas storage purposes where flexibility may enable effective "shrink wrapping" of the trapped molecules.' 

'This work really highlights how reactive these materials can be,' commented Stuart James of Queen's University, Belfast. 'Whereas conformational flexibility is now quite well-known, bond-breaking and a change of topology during gas sorption is much more dramatic.'

Susan Batten