In-situ fabrication of g-C3N4/MIL-68(In)-NH2 heterojunction composites with enhanced visible-light photocatalytic activity for degradation of ibuprofen

For the first time, visible-light-driven g-C3N4/MIL-68(In)-NH2 heterojunction composites with high photocatalytic activity were prepared for the degradation of ibuprofen (IBP) using an in-situ solvothermal synthesis method assisted with ultrasonication. The composites achieved intensive visible-light absorption, enhanced separation efficiency of photogenerated carriers, and high adsorption capacity, thus achieving excellent photocatalytic degradation for IBP. Among all the composites, 10 wt% g-C3N4/MIL-68(In)-NH2 exhibited the maximum photocatalytic rate (0.01739 min−1), 19.28 and 2.00 times higher than those of g-C3N4 and MIL-68(In)-NH2, respectively. Moreover, the pH, ibuprofen concentration, and catalyst dosages played important roles both in photodegradation and adsorption. In addition, the photocatalytic mechanism was also elucidated, demonstrating that h+ was the main reactive species, followed by OH and O2− radicals, responsible for the degradation of IBP. Finally, seven aromatic intermediates of IBP were identified, and five possible degradation pathways were proposed, mainly involving hydroxylation, aldehyde oxidation, decarboxylation, and dehydrogenization reactions.