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.