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.