Construction of NH₂-UiO-66/BiOBr composites with boosted photocatalytic activity for the removal of contaminants

Metal-organic framework (MOF) have gained significant interest for photocatalysis, mainly due to the advantages of the regulable semiconducting characteristics and tunable porous structure. In this work, a novel heterojunction of NH₂-UiO-66/BiOBr composites were successfully synthesized via the growth of BiOBr nanosheets on the surface of these NH₂-UiO-66 octahedrons. The as-prepared composites showed a large interface contact area, which ensured preferable charge carriers transfer between NH₂-UiO-66 and BiOBr. In addition, the increased specific surface area endowed NH₂-UiO-66/BiOBr composites with high adsorption capacity for contaminants. As a consequence, the composites displayed enhanced photocatalytic performance for tetracycline hydrochloride (TC) degradation and Cr(VI) reduction in comparison with BiOBr or NH₂-UiO-66, and the ideal NH₂-UiO-66 content was around 15 wt%. Superoxide radical (O₂ ^{[rad] −}) and holes (h⁺) acted as a key role in the degradation of TC, while electrons (e⁻) and O₂ ^{[rad] −} were the major active groups involved in Cr(VI) reduction owing to reactive-species-quenching experiments and electron spin resonance (ESR) technique. Furthermore, a possible TC degradation pathway was explored based on the mass spectroscopy (MS) analysis. The introduction of MOF into inorganic photocatalysts exhibits a promising strategy to enhance the photoreactivity of the catalysts in the field of water purification.