Mn-Co mixed oxide (MnaCobOX) catalysts were prepared by the precipitation method, and the effect of Mn/Co (atom) on their structural and catalytic performance for the solvent-free selective oxidation of cyclohexane with oxygen was investigated. The results showed that the atomic ratio of Mn/Co would affect the phase constitution, surface area, surface Mn valence states and the reducibility of the MnaCobOX catalysts. When the atomic ratio of Mn/Co in the catalyst is 0.6, the Mn2Co3OX catalyst behaved with excellent catalytic activity and stability, which should be attributed to its high specific surface area and the high atomic ratios of (Mn4++Mn3+)/Mn and Co3+/Co on its surface. The effects of the preparation conditions for the Mn2Co3OX catalyst and the reaction conditions on the selective oxidation of cyclohexane over the Mn2Co3OX catalyst was tested. Under the reaction conditions of 0.5 MPa O-2 and 140 degrees C for 4 h, 10.4% conversion of cyclohexane and 62.0% selectivity to a mixture of cyclohexanone and cyclohexanol (KA oil) were achieved. After this Mn2Co3OX catalyst was repeatedly used 10 times, the cyclohexane conversion and the selectivity to KA oil had hardly changed. (C) 2016 Elsevier B.V. All rights reserved.