Constructing CQDs/MIL-101(Fe)/g-C3N4 photocatalyst and its enhancement to the photocatalytic activity.

• A CQDs/MIL-101(Fe)/g-C 3 N 4 composite photocatalyst was successfully prepared. • The existence of CQDs promoted the movement of photogenerated electrons in CQDs/MIL-101(Fe)/g-C 3 N 4. • Type-II and Z-scheme heterojunctions may be present in the CQDs/MIL-101(Fe)/g-C 3 N 4 composite simultaneously. In this work, CQDs/MIL-101(Fe)/g-C 3 N 4 photocatalyst was facilely fabricated, which exhibited prominent photocatalytic properties for the degradation of methylene blue (MB) aqueous solution. The photocatalytic degradation rate of MB by CQDs/MIL-101(Fe)/g-C 3 N 4 composite material was found to be 124.7 times higher than that of MIL-101(Fe) and 1.3 times higher than that of MIL-101(Fe)/g-C 3 N 4. Based on the different positions of CQDs in the structure, it is proposed that both Type-II and Z-scheme heterostructure models may exist simultaneously in the CQDs/MIL-101(Fe)/g-C 3 N 4 composite material. The enhancement mechanism of CQDs in promoting the migration and separation of visible light-generated carriers in the ternary composite material is under discussion. [ABSTRACT FROM AUTHOR]