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Bi 4 TaO 8 Cl and Bi 4 TaO 8 Cl:Gd 3+ photocatalysts were synthesized by the solvothermal technique. The phase, microstructure, optical properties, and photocatalytic activities were investigated. Both Bi 4 TaO 8 Cl and Bi 4 TaO 8 Cl:Gd 3+ have the singly orthorhombic phase and the flower-like hierarchical structure. The Bi 4 TaO 8 Cl: Gd 3+ has higher photocatalytic activity of MB than that of Bi 4 TaO 8 Cl under visible light irradiation. The higher photocatalytic activity of Bi 4 TaO 8 Cl:Gd 3+ is induced by its lower band gap energy, the higher efficiency charge separation, and transfer process, as well as the photogenerated charge carriers with a longer time, which are confirmed by the longer absorption band edge, lower emission intensity, and higher photocurrent under visible light irradiation. The trapping experiments and electron spin resonance results suggest that˙O 2 − is the predominant active species for the photocatalysis of MB by Bi 4 TaO 8 Cl and Bi 4 TaO 8 Cl: Gd 3+ under visible light irradiation. K E Y W O R D S Bi 4 TaO 8 Cl, Gd 3+ doping, hierarchical structure, methylene blue, photocatalysis