Reactivity of NO₂ with Porous and Conductive Copper Azobispyridine Metallopolymers

We report the reactivity of copper azobispyridine (abpy) metallopolymers with nitrogen dioxide (NO₂). The porous and conductive [Cu(abpy)]${}_n$ mixed-valence metallopolymers undergo a redox reaction with NO₂, resulting in the disproportionation of NO₂ gas. Solid- and gas-phase vibrational spectroscopy and X-ray analysis of the reaction products of the NO₂-dosed metallopolymer show evidence of nitrate ions and nitric oxide gas. Exposure to NO₂ results in complete loss of porosity and a decrease in the room-temperature conductivity of the metallopolymer by four orders of magnitude with the loss of mixed-valence character. Notably, the porous and conductive [Cu(abpy)]${}_n$ metallopolymers can be reformed by reducing the Cu-nitrate species.