Multi-dimensional (2D–3D) assembly of BiOI/BiOBr/UiO-66-NH2 composites to form multi-heterojunction structures for synergistic removal of Rhodamine B

In order to enhance the role of UiO-66-NH2 in the photocatalytic system, the method of loading Bi-based materials to construct heterojunctions was chosen to enhance its photocatalytic ability. In this study, the ternary composite BiOI/BiOBr/UiO-66-NH2 was successfully synthesized, and a double type Ⅱ heterojunction was formed among the three. The successful synthesis and the closely interaction of the composites were proved by a series of characterization. Under simulated visible light, the composite material (UBB3) with a molar ratio of KBr to KI of 1:3 had the best RhB removal performance. The removal rate of Rhodamine B (RhB) can be as high as 99.16 % after 80 min of visible light irradiation. This study also preliminarily explored the direct, efficient and rapid degradation of RhB under visible light without dark adsorption stage. The composite material also had good reusability. The enhancement of visible light utilization and the inhibition of electron(e-)-hole(h+) recombination were the main reasons for the enhancement of photocatalytic activity. In the presence of double heterojunctions, it was found that while the formation of superoxide radicals was involved in the degradation of pollutants, h+ were directly involved in the degradation of RhB as reactants, reducing the reaction procedure. Finally, the photocatalytic mechanism was proposed.