H-Co-silicate having an MFI structure (CoMFI), calcined in steam-containing air at 800 degrees C (CoMFI-800S), was characterized by XRD and diffuse reflectance electron absorption (EA). The calcination educed some of the Co ions from the CoMFI framework to make small clusters nearby. The CoMFI-800S performance in NO elimination in the presence of excess O-2 was compared with that of Co supported on siliceous MFI zeolite ([Co]SiMFI), Co supported on H-Co-silicate ([Co]CoMFI), and a physical mixture of CoMFI and [Co]SiMFI (Co + [Co]). The educed Co ions enhanced NO elimination due to the uniform and isolated dispersion of oxidized Co clusters.