Design of graphitic carbon nitride supported Ag–Cu2O composites with hierarchical structures for enhanced photocatalytic properties

•The nanocomposite is fabricated by two-step reduction procedure at room temperature.•The nanocomposite exhibits enhanced photocatalytic activity for the azo dyes.•The organic molecules are cracked into smaller fragments after reaction.•The holes left in Cu2O crystals are the main reactive species.•The enhanced photocatalytic activity is due to the synergetic effect of Ag and C3N4.