Enhanced photodegradation of acetaminophen over Sr@TiO2/UiO-66-NH2 heterostructures under solar light irradiation

Novel Sr@TiO2/UiO-66-NH2 heterostructures were synthesized by a two-step solvothermal approach and tested as photocatalysts for the solar degradation of acetaminophen. Strontium titanate was used as precursor to obtain the heterostructures, resulting in Sr@TiO2 anchored and dispersed on the UiO-66-NH2. The effect of the Sr@TiO2:UiO-66-NH2 ratio was analyzed. All the heterostructures were more active than the pattern UiO-66NH(2), and the most active achieved more than 90% of conversion of acetaminophen. This enhanced degradation was ascribed to a better separation and faster transfer of charges, as confirmed by photoluminescence and electrochemical characterization. Radical trapping experiments revealed that superoxide radicals (O-2(center dot-)) and to a lower extent photoinduced holes (h(+)) were involved in acetaminophen degradation. As a novelty, the activity and stability of the best photocatalyst were evaluated in a continuous flow reaction system, upgrading conventional short-cycle batch studies. The heterostructure maintained an almost constant high conversion of acetaminophen during the 10 h on stream of the experiment, demonstrating excellent photocatalytic performance and stability in water. Besides, the photocatalytic degradation intermediates were identified, and a corresponding pathway of ACE transformation was proposed.