Heterojunctions Based on BiOBr Nanosheets Decorated on α-Bi2O3 for Photodegradation of Rhodamine B

Photocatalysis is extensively implemented in organic pollutant degradation, and the critical point is to develop outstanding and stable photocatalysts. Herein, the synthesis of coral reef-like α-Bi2O3/BiOBr heterostructure photocatalysts involves the in situ growth of BiOBr nanosheets onto α-Bi2O3, with the latter derived through calcination utilizing a bismuth-based metal–organic framework (CAU-17) as the precursor. Under simulated sunlight, the 20% α-Bi2O3/BiOBr heterojunction degraded nearly 97.7% of RhB in 60 min, while pure α-Bi2O3 and BiOBr nanosheets degraded only 7.8 and 65.3%, respectively. Furthermore, the 20% α-Bi2O3/BiOBr nanocomposite exhibited superior recycling stability, degrading 86.6% RhB after four cyclic experiments. This is attributed to the fact that the nanoscale α-Bi2O3 material obtained by calcination can retain the exoteric diffusion channels of CAU-17, making α-Bi2O3/BiOBr heterojunctions have an enormous specific surface area, providing more adsorption sites and promoting their photocatalytic capacity. Free radical capture tests and electron paramagnetic resonance measurements indicated that h+ and •O2– were the primary active substances during photodegradation. On the basis of that, a feasible photodegradation mechanism of type II α-Bi2O3/BiOBr heterojunctions was proposed. This study opens up the possibility of designing type II heterojunctions with MOFs as precursors for dye degradation.