Ordered mesoporous carbon (OMC)-metal oxide composites have attracted great interest due to their combination of high surface area, uniform pores, good conductivity of mesoporous carbon, and excellent photo-, electro- and chemical sensing properties of metal oxides. Herein, OMC-metal oxide composites with large mesopores and monodispersed CoOx nanoparticles were synthesized via a controllable multicomponent cooperative coassembly of ultrahigh-molecular-weight poly(ethylene oxide)-block-polystyrene (PEO-b-PS) copolymers, resol (soluble phenoic resin carbon precursor), and cobalt nitrate (cobalt oxide precursor). The obtained nanocomposites possess a face-centered cubic (fcc) mesoporous structure, large pore size (13.4-16.0 nm), high surface area (394-483 m2/g), large pore volume (0.41-0.48 cm3/g), and uniform CoOx nanoparticles with tunable diameters (6.4-16.7 nm). The long chain length of amphiphilic PEO-b-PS template molecules contributes to large mesopores and thick pore walls that allow a controllable nucleation of metal oxides and the formation of CoOx nanoparticles that are partially embedded and stabilized in the graphitic carbon walls and semiexposed in the mesopore channels, avoiding pore blockage and facilitating the mass transportation of guest molecules. The in situ loaded highly dispersed CoOx nanoparticles promote the graphitization of carbon frameworks during the pyrolysis procedure at relative lower temperatures (∼700 °C). Due to the strong synergistic effect between the graphitic OMC with large pores and uniform active p-type CoOx nanoparticles, the obtained mesoporous nanocomposite exhibit superior performance in hydrogen sensing.