Boosted Activity of g-C3N4/UiO-66-NH2 Heterostructures for the Photocatalytic Degradation of Contaminants in Water

• Published in: International journal of molecular sciences 2022-11, Vol.23 (21), p.12871
• Main Authors: Solís, Rafael R., Quintana, María Alejandra, Martín-Lara, María Ángeles, Pérez, Antonio, Calero, Mónica, Muñoz-Batista, Mario J.
• Format: Article
• Language: English
• Subjects: Acetaminophen; Analgesics; Aqueous solutions; Carbon; Carbon nitride; Catalytic activity; Contaminants; Degradation; graphitic carbon nitride; Heterostructures; Ligands; Luminescence; Metal-organic frameworks; Optoelectronics; Oxidation; Photocatalysis; Photodegradation; Photoluminescence; Photons; Pollutants; Quantum efficiency; Radiation; Semiconductors; UiO-66-NH2; Water treatment
• ISSN: 1422-0067; 1661-6596; 1422-0067
• DOI: 10.3390/ijms232112871

The combination of graphitic carbon nitride and the metal-organic framework UiO-66-NH2 has been developed with the aim to enhance the photocatalytic activity of pure semiconductors. Different proportions of g-C3N4 and UiO-66-NH2 were combined. Complete characterization analysis of the resulting photocatalytic materials was conducted, including N2 adsorption isotherms, XRD, FTIR, STEM-EDX microscopy, DRS-UV-visible, and photoluminescence. The photocatalytic activity was tested in an aqueous solution for the removal of acetaminophen as the target pollutant. From the obtained results, less than 50% of UiO-66-NH2 incorporated in the g-C3N4 structure enhanced the photocatalytic degradation rate of both bare semiconductors. Concretely, 75% of g-C3N4 in the final g-C3N4/UiO-66-NH2 heterostructure led to the best results, i.e., complete acetaminophen elimination initially at 5 mg·L−1 in 2 h with a pseudo-first order rate constant of ca. 2 h−1. The presence of UiO-66-NH2 in the g-C3N4 enhanced the optoelectronic properties, concretely, the separation of the photo-generated charges was improved according to photoluminescence characterization. The better photo-absorption uptake was also confirmed by the determination of the quantum efficiency values of the heterostructure if compared to either pure g-C3N4 or UiO-66-NH2. This photocatalyst with the best activity was further tested at different pH values, with the best degradation rate at a pH close to the pHpzc ~4.15 of the solid. Sequential recycling tests demonstrated that the heterostructure was stable after five cycles of use, i.e., 15 h. A high contribution of photo-generated holes in the process of the degradation of acetaminophen, followed marginally by superoxide radicals, was suggested by scavenger tests.