[en] Serials Sm doped Bi₂MoO₆ photocatalyts with different Sm contents (xSm-Bi₂MoO₆, x% = 0.0%, 0.4%, 0.6%, 0.8%, 1.0%, 1.2%) were prepared via hydrothermal method to improve the photocatalytic performance of pure Bi₂MoO₆. The samples are characterized by XRD, XPS, SEM, TEM, HRTEM, and PL techniques. It indicates that Sm³⁺ ions were successfully doped into Bi₂MoO₆, and the band gap value was gradually decreased with Sm dopant concentration increasing. The photocatalytic activity of Sm-doped Bi₂MoO₆ photocatalyst was significantly affected by the Sm doping content. Compared to pure Bi₂MoO₆, the Sm-doped Bi₂MoO₆ samples exhibited much higher photocatalytic activity and 0.8% Sm-doped Bi₂MoO₆ shows the highest RhB photodegradation rate, being 89% in 50 min under visible light irradiation. The improved photocatalytic activity of Sm-doped Bi₂MoO₆ could be attributed to the enhanced visible light absorption, narrower band gaps and higher separation rate of electron-hole pairs derived from Sm trapping photogenerated electrons. But the phase structure, special surface areas and morphology have little effects on the higher photocatalytic activity of Sm-doped Bi₂MoO₆. - Highlights: • The Sm-doped Bi₂MoO₆ can be successfully synthesized by solvothermal method. • The 0.8Sm-BiVO₄ exhibited the highest photocatalytic activity. • The higher activity is due to elevated separation rate of electron-hole pairs. • h⁺ and .·O₂⁻ are the dominant reactive species for the RhB photodegradation