The long-lived electron transfer state of the 2-phenyl-4-(1-naphthyl)quinolinium ion incorporated into nanosized mesoporous silica-alumina acting as a robust photocatalyst in water.

A simple electron donor-acceptor linked dyad, the 2-phenyl-4-(1-naphthyl)quinolinium ion (QuPh(+)-NA), was incorporated into nanosized mesoporous silica-alumina to form a composite, which is highly dispersed in water and acts as an efficient and robust photocatalyst for the reduction of O2 by oxalate to produce hydrogen peroxide with a quantum yield of 10%.