Copper substituted cobalt ferrite Cu1-XCoXFe2O4 (0 <= x <= 1) have been synthesized using sol-gel auto combustion method with citric acid as fuel. Structural identification, magnetic and catalytic properties were investigated using thermogravimetric and differential thermal analysis, X-ray diffraction, scanning electron microscopy, transmission electron microscopy, vibrating sample magnetometry and their application in the selective catalytic reduction of NOx were studied. Analysis of structural properties reveals that all samples have cubic spinel structure. Room temperature magnetic hysteresis measurements as a function of magnetic field infer that the magnetic properties decrease with Cu2+ doping which may be due to the difference of the magnetic moment of Cu2+ and Co2+ ions. The higher activity of the samples in NO selective reduction to N-2 occurs at 350 degrees C, reaching a maximum of 38% NO conversion and 95% of selective conversion to N-2. The compositions containing both Cu2+ and Co2+ ions are more active to the products selectivity to N-2, suggesting a synergistic effect on the active surface of ferrite and the effect of Co2+ is more pronounced than Cu2+ towards NO conversion. (C) 2012 Elsevier B.V. All rights reserved.