Photocatalytic Activity of Novel Tin Porphyrin/TiO2 Based Composites

Three dichloro Sn(IV) porphyrins, trans-dichloro[5,10,15,20-tetra-[2 or 3 or 4-(3-phenoxy)-propoxy]phenyl porphyrin]tin(IV) and the corresponding dihydroxo Sn(IV) porphyrins trans-dihydroxo[5,10,15,20-tetra-[2 or 3 or 4-(3-phenoxy)-propoxy]phenyl porphyrin]tin(IV) were synthesized and characterized spectroscopically. The dihydroxo Sn(IV) porphyrin-TiO2 composites were also prepared and characterized, and an interaction between TiO2 and tin porphyrin molecules involving the axial -OH ligand with the TiO2 surface was proposed. The photocatalytic activity was investigated by testing the photodegradation of 4-nitrophenol (4-NP) in aqueous solution under both visible and UV-vis light irradiation. It was found that the distinct space tropisms of peripheral substituents in meso sites of the porphyrin ring lead to different efficiencies in photodegrading the 4-NP.