A facile strategy has been developed to fabricate Cu(OH)(2) supercages (SCs) as an artificial enzyme system with intrinsic peroxidase-mimic activities (PMA). SCs with high catalytic activity and excellent recyclability were generated via direct conversion of amorphous Cu(OH)(2) nanoparticles (NPs) at room temperature. More specifically, the process that takes a single nanoparticle to a 3D supercage involves two basic steps. First, with addition of a copper ammonia complex, the Cu2+ ions that are located on the surface of amorphous Cu(OH)(2) NPs would evolve into a fine lamellar structure by coordination and migration and eventually convert to ID nanoribbons around the NPs. Second, accompanied by the migration of Cu2+, a hollow cavity is generated in the inner NPs, such that a single nanoparticle eventually becomes a nanoribbon-assembled 3D hollow cage. These Cu(OH)(2) SCs were then engineered as an artificial enzymatic system with higher efficiency for intrinsic PMA than the peroxidase activity of a natural enzyme, horseradish peroxidase.