A promising photocatalyst with favorable visible-light absorption and efficient charge separation is desirable for environmental protection. In this study, orderly nanosheets of binary bismuth oxyhalides (BiOI0.5Cl0.5) doped with the rare earth metal ion Er3+ were immobilized on Ni foam by a facile one-step solvothermal method. The photocatalytic performance of the obtained photocatalyst (Ni [email protected]) was investigated. The effects of Er3+-doping on BiOI0.5Cl0.5 and the photocatalyst loading amount on Ni foam were systematically studied. Ni foam, which is a self-standing conducting 3D skeleton, enhanced the efficiency of the separation of the photogenerated electrons and holes. The Er3+ doped in BiOI0.5Cl0.5 also accelerated the separation of the photogenerated electron-hole pairs by creating abundant oxygen vacancies and surface defects for electron trapping and pollutant adsorption. Consequently, Er3+ doping and immobilization on Ni foam synergistically enhanced the photocatalytic activity of Ni [email protected]. Photocatalytic degradation experiments of Acid Redl were carried out, and the photocatalytic efficiency of Ni [email protected] was found to be enhanced by 1.5 times compared to that of pure BiOI0.5Cl0.5. In addition, the photocatalyst could be easily recycled several times with good stability. Remarkably, the photocatalytic activity of BiOI0.5Cl0.5 is enhanced by effectively doping Er3+ into binary bismuth oxyhalides rather than synthesizing upconversion nanoparticles, and the directly doped Er3+ could react with photoexcited electrons to generate superoxide radicals. So we give a facile way to prepare a rare-earth doped semiconductor photocatalyst that is reusable, recyclable and highly efficient for photodegradation of organic dye from water.