We report a new, surfactant-free method to produce Co3O4 nanocrystals with controlled sizes and high dispersity by caging templation of nanoporous networks. The morphologies of Co3O4 nanoparticles differ from wires to particulates by simply varying solvents. The composites of nanoparticles within network polymers are highly porous and are promising for many applications where accessible surface and aggregation prevention are important. The electrochemical performance of the composites demonstrates superior capacity and cyclic stability at a high current density (∼980 mA h g−1 at the 60th cycle at a current density of 1000 mA g−1). In a catalytic oxidation reaction of carbon monoxide, the composites exhibit a remarkable stability (in excess of 35 hours) and catalytic performance (T100 = 100 °C).