Chloro(2,2':6',2''-terpyridine)platinum(II) ([Pt(tpy)Cl]Cl) complex was successfully anchored to a series of (3-aminopropyl)trimethoxysilane-modified mesoporous silica materials (MCM-41, SBA-15, and MCM-48). Pt LIII-edge x-ray absorption fine structure (XAFS) measurements reveal that the Pt complex reacts with amino groups anchored on the mesoporous silica to create a new Pt-N bond. Upon anchoring, the nonemissive Pt(II) complex exhibits strong photoluminescence at room temp., which is maximized near 530 nm due to ligand-centered (3LC) and/or metal-to-ligand charge transfer (3MLCT) transitions. The intensities of the emission increase in the order of MCM-41 < SBA-15 < MCM-48. In the case of MCM-48, the emission intensity is the highest at 0.42 wt % Pt loading, while concn. quenching is obsd. accompanied with a new emission due to the metal-metal-to-ligand charge-transfer (3MMLCT) transition at high Pt loading. These results correspond well with the photocatalytic activities in the selective oxidn. of styrene derivs. using mol. oxygen (O2). It can be supposed that the enhanced excitation rate and quantum efficiency of the anchored Pt complex, due to the differences in nanoconfinement, increase the energy and/or electron transfer to O2, which ultimately enhances the photooxidn. activity. The 3D-connected channel structure of the MCM-48 silica also accounts for the high photocatalytic activity, where the diffusion of O2 toward the anchored Pt complex occurs smoothly compared to the one-dimensional MCM-41 and SBA-15 silicas, as demonstrated by the quenching rate consts. obtained from Stern-Volmer plots. [on SciFinder(R)]