Developing catalysts with high cost-efficiency, good oxidation activities and strong thermal resistance is an ongoing task. Herein, we present the design and synthesis of confined catalysts with Ag protected by alumina. Thermal treatment at 800 degrees C for 10 h caused neither silver loss nor deactivation of this catalyst. Instead, nanoparticles of Ag formed because of the heat/O-2-derived ripening. These highly dispersed silver species and the catalyst's mesoporous structure worked in tandem to achieve good catalytic performance for oxidation reactions, which made the aged sample a good candidate as CO elimination and gasoline particulate filter catalysts.