Soft Crystals Soak Up Carbon Monoxide

Steel factories belch huge amounts of carbon monoxide as a by-product of the metal-making process. But because the CO is mixed with other gases, such as nitrogen, it can’t be used directly as a feedstock for preparing polymer fibers or plastics. Chemists in Japan may have found a solution to this problem by creating a soft nanoporous crystalline material capable of selectively sequestering CO from other gases and then releasing it easily (Science 2013, DOI: 10.1126/science.1246423). The material, developed by Kyoto University’s Susumu Kitagawa, Ryotaro Matsuda, and coworkers, is composed of 5-azidoisophthalate groups and divalent copper(II) cations. The Cu²⁺ ions weakly associate with CO. As the CO binds, the material’s framework opens to accommodate more CO. The researchers showed that the porous material could be used to enrich a mixture of equal amounts of CO and N₂ to 94% CO.