Methyl-lined pores trap simple alkanes

A new type of designed material containing pores lined with methyl groups has been shown by François P. Gabbaï and his research group at Texas A&M University to reversibly adsorb simple alkanes at room temperature (Angew. Chem. Int. Ed., DOI: 10.1002/anie. 200602440). The compound could become the basis of a class of materials useful for separating or storing volatile hydrocarbons, the researchers note. Materials with columnar pore structures that can trap alkanes have been made before, Gabbaï adds, but the pores of those materials typically are lined with aromatic groups. The researchers made the new material by mixing a tris(alkynyl)benzene compound, [(CH₃)₃SiC≡C]₃C₆H₃, with a trimeric perfluorophenylene-mercury complex, (HgC₆F₄)₃. These molecules aggregate into extended stacks (shown; orange = Hg, purple = Si, green = F, gray = C) to form a honeycomb structure with the silyl methyl groups pointing into the pores. The team measured adsorption of up to 2.9 wt % for alkanes ranging from methane to n-hexane. The alkanes can be desorbed under vacuum without any structural changes to the starting material.