Immobilization of luminescent Platinum(II) complexes on periodic mesoporous organosilica and their water reduction photocatalysis

[Display omitted] •Luminescent Pt(II) complexes were immobilized on periodic mesoporous organosilica (PMO).•Immobilized Pt(II) complexes show slightly red-shifted absorption bands on PMO.•Pt(II)-complex luminescence is quenched when the luminescence originates from the 3ππ* excited state of the bipyridine moiety.•PMO-immobilized Pt(II) complexes photosensitize water reduction. Pt(II) complexes have been immobilized on a periodic mesoporous organosilica (PMO) consisting of 2,2′-bipyridine (bpy) units bridged by siloxane bonds (BPy-PMO). Although these Pt(II) complexes are luminescent in their discrete molecular states, the luminescence properties of the immobilized complexes largely depend on the origin of the emission; luminescence is quenched when the emission originates from the 3ππ* excited state of bipyridine due to the coupling of the CH bending vibration of the bpy and the Si-O stretching vibration of the siloxane framework, while luminescence is maintained when the 3ππ* excited state of bipyridine is not the lowest excited state. Although the simple coexistence of Pt(0) nanoparticles and Pt(II) complexes did not catalyze water reduction even in the presence of an electron relay, photocatalytic water reduction is observed when Pt(0)/Pt(II)-co-immobilized BPy-PMOs are used. This result clearly demonstrates the importance of the integration of photosensitizers and catalysts on the PMO for enhancing intermolecular electron-transfer processes.