Chlorinated volatile organic compounds (CVOCs) existing widely in the industries are harmful to the environment and human’s health. It is urgent to develop highly efficient catalysts for their combustion. Herein, a series of porous MnOx/Co3O4 nanocomposites are synthesized by the pyrolysis of Mn@Co-ZIF-67 precursors, in which the Mn ions are introduced by impregnation method. XRD, Raman, ICP-OES, BET, SEM, TEM, XPS, O2-TPD, and H2-TPR have been performed to investigate the as-prepared catalysts’ physicochemical properties. The optimal catalyst MnOx/Co3O4-4h exhibits 90% and 100% chlorobenzene (CB) conversion (1000 ppm, Air, WHSV = 60,000 mL/(g h)) at 334 °C and 350 °C, respectively. And the better catalytic performance over MnOx/Co3O4-4h compared with the pure Co3O4 and other MnOx/Co3O4 nanocomposites mainly ascribes to its porous structures, homogeneous dispersion, optimal Mn/Co molar ratio, more lattice defects, and higher surface OLatt/OAds ratio. Meanwhile, MnOx/Co3O4-4h displays high stability and resistance to moisture. Main intermediates have been further investigated by in situ DRIFT, and the degradation mechanism has been proposed according to the analysis of intermediates.