Sulfur-modulated metal–organic framework MIL-101(Fe) with CQDs anchored as an efficient light-driven photocatalyst: photocatalytic performance and mechanism investigation

The production of abundant free radicals and the effective separation of photo-induced carriers are considered challenging by researchers for the application of photocatalytic technology in the field of wastewater purification and environmental remediation. Herein, we successfully synthesized a novel S-MIL-101(Fe)@CQD composite via multi-step synthetic routes involving a simple solvothermal synthesis method and annealing treatment process to remove both Cr6+ and dyes in wastewater. A series of characterization methods and photocatalytic property tests were performed, proving that the synthesized S-MIL-101(Fe)@CQDs exhibited higher photocatalytic activity than MIL-101(Fe), which is mainly due to the formation of an intramolecular energy level and modulation of the intrinsic electronic properties of the MOF, where the CQDs act as an electron acceptor. We proposed the underlying photocatalytic mechanism through trapping experiments of the active species. Also, we performed several typical pollutant degradation experiments and confirmed the wide applicability of this composite. In summary, this work provides new insight into the construction of modified MOFs for the efficient removal of toxic pollutants from water.