Organic polymers woven into a 3D framework offer a new way of making flexible materials with tunable properties.

Covalent organic frameworks are highly porous structures with many promising applications, but they are typically rigid. Omar Yaghi of the University of California, Berkeley, Osamu Terasaki of Stockholm University and their colleagues created such a framework, dubbed COF-505. It is made of individual building blocks of copper ions that carry fragments of a polymer. Joining these units together with linear molecules formed crystals with the same tetrahedral geometry as diamond.

The researchers then removed the copper ions to leave interwoven, helical polymer threads that were collectively ten times more elastic than the precursor. The copper ions could also be replaced, raising the possibility of loading the polymer weave with metal catalysts, or of using it to absorb metal ions from liquid waste.

Science 351, 365–369 (2016)