Nitrogen dioxide (NO2) is a toxic air pollutant, and efficient abatement technologies are important to mitigate the many associated health and environmental problems. Here, we report the reactive adsorption of NO2 in a redox-active metal-organic framework (MOF), MFM-300(V). Adsorption of NO2 induces the oxidation of V(III) to V(IV) centers in MFM-300(V), and this is accompanied by the reduction of adsorbed NO2 to NO and the release of water via deprotonation of the framework hydroxyl groups, as confirmed by synchrotron X-ray diffraction and various experimental techniques. The efficient packing of {NO2·N2O4}∞ chains in the pores of MFM-300(VIV) results in a high isothermal NO2 uptake of 13.0 mmol g-1 at 298 K and 1.0 bar and is retained for multiple adsorption-desorption cycles. This work will inspire the design of redox-active sorbents that exhibit reductive adsorption of NO2 for the elimination of air pollutants.