Significant effects of negligible amount of H2O2 on photocatalytic efficiency of MIL-125 and NH2-MIL-125 nanostructures in degradation of methylene blue

Abstract

The notable impact of a trace amount of hydrogen peroxide (H₂O₂) on the photocatalytic performance of Ti-based metal–organic frameworks (MOFs), namely MIL-125 and NH₂-MIL-125, in the purification of water polluted with chemical agents was studied experimentally. MIL-125 and NH₂-MIL-125 were synthesized using the solvothermal method and were characterized by a variety of diagnostic methods. NH₂-MIL-125 exhibited a bandgap of 2.8 eV compared to 3.65 eV for MIL-125 with optimal visible light capture capability, indicating the outstanding photodegradation activity of the synthesized MOFs. In addition, the photocatalytic performance of MIL-125 and NH₂-MIL-125 was tested for the degradation of methylene blue (MB) as a chemical pollutant in water under both dark conditions and irradiation by visible light and a UVC lamp. NH₂-MIL-125 exhibited a significantly higher photodegradation rate compared to MIL-125 due to the presence of the amino group, higher surface electronegativity and slightly lower bandgap. Furthermore, the effect of H₂O₂ as an electron acceptor on the efficiency of MB degradation was investigated, which markedly enhanced the photocatalytic MB degradation performance due to the ligand-to-metal charge transfer mechanism, particularly for NH₂-MIL-125, under all tested conditions.