Construction of heterojunction is an effective strategy to conquer the severe charge carrier recombination limitation of single component g-C3N4 photocatalyst. In the present work, novel heterojunctions composed of g-C3N4 nanosheets and Sr0.4H1.2Nb2O6 center dot H2O nanooctahedrons were constructed via a simple hydrothermal method. The as-prepared Sr0.4H1.2Nb2O6 center dot H2O/g-C3N4 (HSN/CN) heterojunction showed high photocatalytic activity in the water splitting reactions. Specially, it is found that the developed 20 wt%-HSN/CN heterojunction shows high water splitting activity with H-2 evolution rate up to 469.4 mu mol g(-1), which was much higher than that of bare CN. This enhanced photocatalytic activity for H-2 evolution can be mainly attributed to the matched energy level and heterojunction structure which could improve the photo-generated charge carriers separation and transfer. This work implies that construction of heterojunctions with a wide band gap semiconductor is a feasible strategy for enhancement of photocatalytic activity of CN materials. (C) 2018 Elsevier Inc. All rights reserved.