Metal-Free Porphyrin-Sensitized Mesoporous Titania Films For Visible-Light Indoor Air Oxidation

Transparent cubic mesoporous TiO(2) films coated on soda-lime glass have been developed. A metal free meso-tetrakis(4-sulfonatophenyl) porphyrin (TPPS) has been adsorbed on these TiO(2) films from aqueous solutions. The results indicated that the obtained mesoporous TiO(2) and 3D TPPS/TiO(2) films are optically transparent and crack free (thickness ca. 200 +/- 20 nm). The introduction of the TPPS molecules has only a very small influence on the pore system and some limited pore blocking seems to occur. Transmission electron microscopy (TEM) images revealed that the adsorption of TPPS does not disrupt the meso order of TPPS/TiO(2). The particle size of these TiO(2) nanocrystals has been measured to be approximately 5-8 nm. TPPS/TiO(2) photocatalysts, exhibiting regularly ordered meso-pores, large surface area (ca. 102.5 cm(2)cm(-2)), and specific pore volume of about 0.1 mm(3)cm(-2), show improved light-harvesting efficiency as compared with other transparent TiO(2) films. Employing the 3D TPPS/TiO(2) photocatalyst, a quantum efficiency of 0.059% has been obtained for the photodegradation of CH(3)CHO in the gas phase under visible-light illumination. Recycling tests demonstrated that the newly synthesized photocatalyst was quite stable during this gas-solid heterogeneous photocatalytic process because no significant decrease in photocatalytic activity was observed even after being used repetitively up to five times. Therefore, the newly synthesized transparent 3D TPPS/TiO(2) photocatalysts can potentially be applied for low-cost air purification and self-cleaning applications.