Cyclometalated platinum(II) complex has been successfully incorporated into the (3-aminopropyl) triethoxysilane-modified channels of ordered mesoporous silica SBA-15 that has large pore hexagonal channels. Studies on the O-1(2) generation conclusively demonstrates that the olefins in the nano-channels of SBA-15 can be enriched 8 times higher than those in the homogeneous solution as the diffusion quantum yield of singlet oxygen (O-1(2)) is assumed to be unit. The platinum( II) complex loaded in the channel of SBA-15 is stable, and the photosensitized oxidation occurs efficiently. No obvious degradation and leaching of photosensitizers is observed even after 10 runs. Only a simple filtration is needed for the recycled use of the expensive noble metal catalysts. This versatile system is a good example of photochemical reactions occurring in the mesoporous silica molecular sieve. SBA-15 not only provides a support for the photosensitizer, but also acts as a nano-reactor to facilitate the photooxidation.