Hydroxyl-graphene quantum dots (GQDs) modified mesoporous graphitic carbon nitride (mpg-C3N4) composites were fabricated through electrostatic interactions. A variety of techniques were applied to discuss systematic effect on the morphology, optical, electronic properties and structure of GQDs/mpg-C3N4 composites. Remarkably, the 0.5 wt% GQDsimpg-C3N4 composites exhibited higher photocatalytic activity than that of the pure mpg-C3N4 by using rhodamine B (RhB) and colorless tetracycline hydrochloride (TC) as pollutants under visible light irradiation. The results indicated that uniform dispersion of GQDs on the surface of mpg-C3N4 and intimate contact between the two materials contributed to the enhanced activity. Radical trapping experiments and electron spin resonance tests both certified that the GQDsimpg-C3N4 composites can generate more center dot O-2(-) species and a small fraction of holes for photocatalytic degradation. (C) 2017 Elsevier B.V. All rights reserved.