Eco-friendly TiO2–AC Photocatalyst for the Selective Photooxidation of 4-Chlorophenol

The influence of surface pH of activated carbon on selectivity of TiO₂ during the photooxidation of 4-chlorophenol on UV-irradiation was studied. Chlorine substitution by p-hydroxylation yielding hydroquinone in equilibrium with benzoquinone and o-hydroxylation to 4-chlorocathecol were detected as the main intermediates in the photooxidation of 4CP. Changes in surface pH of carbons from basic to closely neutral induce a remarkably increase in the production of 4-chlorocatechol by a factor of 22 on TiO₂–AC in comparison of TiO₂ alone. A mechanism of interaction between both solids is proposed to explain changes both in photoactivity and photoselectivity of TiO₂. In conclusion, results showed that TiO₂–AC can be used as an alternative green photocatalyst in organic synthesis.