Résumé
A silylated porphyrin derivative is co-hydrolyzed with Ti(OiPr)4 to produce a hybrid TiO2 photocatalyst, and three different ratios between porphyrin and TiO2 are made. In this way, the porphyrin fragments are held in the resulting matrix through strong Si-O-Ti covalent bonds to limit porphyrin leaching. Thanks to its photoactive character the porphyrin fragment can act as an actuator for the TiO2 to degrade organic pollutants using light from ultraviolet to the visible range. The photocatalysts are synthesized using an easy aqueous route allowing "green conditions" for synthesis. For comparative purposes, the corresponding pure TiO2 and a grafted catalyst are also synthesized and studied. For all samples, a mixture of anatase/brookite TiO2 is obtained, resulting in crystalline materials with low temperature synthesis. The three porphyrin-doped samples prepared in water prove to be efficient photocatalysts for the degradation of p-nitrophenol (PNP) under visible light, and an improvement in photoactivity is observed when the amount of porphyrin increases. The photocatalyst activity is very stable over time as the PNP degradation remains nearly constant after 264 h of testing, showing no leaching of porphyrin. In recycling tests, the grafted sample presents bond breaking between POR-Si and TiO2 and a decrease in photoactivity towards pure TiO2 sample activity. A comparison with the commercial Evonik P25 catalyst shows that the porphyrin-doped TiO2 is nearly 6 times more photoactive under visible light for PNP degradation.