Facile fabrication of novel Z-scheme g-C3N4 nanosheets/ Bi7O9I3 photocatalysts with highly rapid photodegradation of RhB under visible light irradiation

•Novel gCNNS/Bi7O9I3 nanocomposites were introduced for cationic and anionic dyes degradation under visible light.•The gCNNS/Bi7O9I3 (15%) nanocomposite represented optimum photocatalytic efficiency in Rhodamine B (RhB), Congo red (CR), and malachite green (MG) photodegradation•The RhB photodegradation during 20 min of the irradiation was 19.7 and 15.5 folds higher than bulk g-C3N4 and g-C3N4 nanosheets samples, respectively.•The fabrication method of the prepared nanocomposite was modest and cost-effective.•The as-obtained photocatalyst exhibited excellent stability and recyclability towards photodegradation of dyes.