NOx sorption/desorption capacities of Oxi-Anionic materials were measured under representative exhaust gas mixture conditions at 300 degrees C, with a NOx trap containing CaO and CuOx impregnated over a commercial gamma-Al2O3. These systems absorb (or adsorb) NOx in a gas stream containing both CO2 at 300 degrees C. In the case of a thermal desorption, the trapped NOx should desorb at a temperature below 550 degrees C.