[en] Highlights: • Hierarchical porous Bi₂₄O₃₁Br₁₀ were fabricated via an ion-exchange approach. • The sample exhibited excellent adsorption and photocatalytic performance. • The enhanced performance can be ascribed to the structural feature of Bi₂₄O₃₁Br₁₀. Construction of hierarchical structure assembled by ultrathin nanosheet is one of the important challenges in material chemistry and photocatalytic field, because this kind of material can combine the advantages of hierarchical structure and ultrathin material. Herein, we propose an ion-exchange approach to the fabrication of novel hierarchical porous Bi₂₄O₃₁Br₁₀ microstructures assembled by ultrathin nanosheets with thicknesses of 3–5 nm through a facile reflux process, employing previously-prepared Bi₂₅VO₄₀ micro-cubes as precursors of Bi^{3 +} ions. Experiments revealed that the Bi₂₄O₃₁Br₁₀ hierarchical structures possessed a high surface area (~ 67.16 m²/g) and abundant mesopores, leading to the strong adsorption capacity for rhodamine B (RhB) with high concentration. The maximal adsorption quantity of the product was calculated to be 24.4 mg/g. Photocatalytic results demonstrated that the as-prepared Bi₂₄O₃₁Br₁₀ sample exhibited a significant structure-induced enhancement of photocatalytic performance. After 12 min of UV–visible-light irradiation, 96% of RhB solution (40 mg/L) could be completely decomposed. In addition, the trapping experiments confirmed that photo-generated hole was believed as the chief active specie in the degradation process of RhB molecule.