Z-Scheme BiOBr/Ti-MOF Nanosheet Heterojunction for Enhanced Visible-Light-Driven Pollutants Degradation

A Z-scheme photocatalyst could enhance charge separation and extend the photocatalytic activity under visible light, improving the efficiency of pollutant degradation and other photochemical processes. In this study, a low-energy, high-performance Z-scheme BiOBr/NH₂-MIL-125 (Ti) nanosheet (BiOBr/Ti-MOF NS) heterojunction photocatalyst was efficiently synthesized through a simple solvothermal method. Under visible light irradiation, the photodegradation rate constant of BiOBr/Ti-MOF NS for Rhodamine B (RhB) (<i>k</i> = 0.403 76 min^-1) was greater than that of pure BiOBr (<i>k</i> = 0.089 75 min^-1) and NH₂-MIL-125 (Ti) (<i>k</i> = 0.071 67 min^-1). The photodegradation rate constant (<i>k</i> = 0.015 58 min^-1) of hexavalent chromium (Cr(VI)) was also significantly higher than that of pure BiOBr (<i>k</i> = 0.001 70 min^-1) and NH₂-MIL-125 (Ti) (<i>k</i> = 0.003 72 min^-1). RhB was completely degraded within 6 min, while the reduction efficiency of Cr(VI) reached 79.0% within 100 min. Furthermore, the possible photocatalytic degradation mechanism of RhB in the BiOBr/Ti-MOF NS composites is proposed based on structural analysis and radical quenching experiments. The remarkable enhancement in photocatalytic performance can be attributed to its optimized band structure, accelerated charge carrier transport and separation, strong interfacial interaction, and increased adsorption capacity for pollutants. This study offers valuable insights for designing highly efficient Z-scheme heterojunction photocatalysts for pollutant removal.