A network of cubes opens the door for new COF chemistry

Covalent organic frameworks (COFs) offer many of the benefits of metal-organic frameworks (MOFs) yet haven’t kept pace with the growing number of complex architectures achieved by their metal-containing counterparts. But a new COF created by researchers at the University of California, Berkeley, opens the door for organic frameworks with higher connectivity than ever before. Previous COF architectures were limited by the geometry of carbon atoms, says Omar M. Yaghi , a materials chemist who led the study. Inspired by 3-D structures made by borophosphonate bonds, Yaghi’s team designed a borophosphonic acid linker with a boron group on one end of a phenyl ring and a phosphorus group on the other. When the linker is heated in solution with a modulator that controls the reaction rate, a COF of repeating borophosphate cubes self-assembles ( Science 2020, DOI: 10.1126/science.abd6406 ). “It’s almost like a jigsaw puzzle piece,” Yaghi says. “When eight of