Composite photocatalysts with nanoflower-structured MoS2 grown on pyridine-modified graphitic carbon nitride (g-C3N4) have been synthesized through a facile in situ solvothermal approach. These composites demonstrate greatly enhanced response to visible light, and consequently remarkably enhanced hydrogen evolution performance by photocatalytic water splitting. The addition of 2,5-dibromopyridine during the formation process of g-C3N4 can not only enhance the photocatalytic activity but also the durability of the photocatalysts. The MoS2 content and the ratio between 2,5-dibromopyridine and g-C3N4 in these composites can be well tuned to obtain the optimized photocatalytic activity with a peak H-2 production rate of 25 mu mol h(-1) on 50 mg photocatalyst without adding any noble metal under visible light irradiation at 283 K. A dual synergetic mechanism in MoS2/pyridine-modified g-C3N4 composite, which is featured with significantly promoted separation of photo-generated carriers and stability of S2- and/or S-2(2-) in the composites under visible light irradiation, has been proposed to account for the distinguished hydrogen evolution activity and stability of these composite photocatalysts. (C) 2016 Elsevier B.V. All rights reserved.