Degradation of diclofenac in water under LED irradiation using combined g-C₃N₄/NH₂-MIL-125 photocatalysts

This study reports the photocatalytic degradation of diclofenac by hybrid materials prepared by combination of graphitic carbon nitride (g-C₃N₄) and titanium-metal organic framework (NH₂-MIL-125), in different mass proportions (MOF:C₃N₄ of 25:75, 50:50 and 75:25). The hybrid materials were fully characterized, and their properties compared to those of the individual components, whose presence was confirmed by XRD. The porous structure was the result of the highly microporous character of the MOF and the non-porous one of g-C₃N₄. The band gap values were very close to that of MOF component. Photoluminescence measurements suggested an increase on the recombination rate associated to the presence of g-C₃N₄. Photodegradation tests of diclofenac (10 mg·L^-1) were performed under UV LED irradiation at 384 nm. The hybrid materials showed higher photocatalytic activity than the individual components, suggesting the occurrence of some synergistic effect. The photocatalyst with a MOF:g-C₃N₄ ratio of 50:50 yielded the highest conversion rate, allowing complete disappearance of diclofenac in 2 h. Experiments with scavengers showed that superoxide radicals and holes played a major role in the photocatalytic process photodegradation, being that of hydroxyl radicals less significant. From the identification of by-products species, a degradation pathway was proposed for the degradation of diclofenac under the experimental operating conditions.