Heterojunctions of graphitic carbon nitride (g-C3N4) and Bi2MoO6 were solvothermally synthesized and characterized by X-ray diffraction, Fourier transform-infrared spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy (TEM) and high resolution TEM. The photocatalytic degradation activity of the g-C3N4/Bi2MoO6 composites for Rhodamine B was examined under visible light irradiation. The heterojunction composites exhibited higher photocatalytic activity than pure g-C3N4 or Bi2MoO6. The photocatalytic activity of the composites increased then decreased with increasing Bi2MoO6 content. The g-C3N4/Bi2MoO6 heterojunction with a Bi2MoO6 content of 16.1 wt.% exhibited the highest photocatalytic activity, and its photocatalytic efficiency was more than three times those of pure g-C3N4 or Bi2MoO6. The enhanced photocatalytic activity of the g-C3N4/Bi2MoO6 heterostructure photocatalyst was attributed predominantly to the efficient separation of photoinduced electrons and holes. The g-C3N4/Bi2MoO6 heterojunction photocatalyst exhibited excellent stability and reusability. A detailed mechanism for the enhanced photocatalytic activity is discussed. Superoxide radicals were the major active species. This study provides a visible light responsive photocatalyst with potential in environmental remediation applications. (C) 2014 Elsevier B.V. All rights reserved.