In situ constructed TiO2/MIL-100(Fe) heterojunction with accelerated Fe3+/Fe2+ cycle for enhanced photo-Fenton degradation of methyl blue

The efficient removal of persistent anionic organic dyes from industrial wastewater remains challenging, owing to rapid charge-carrier recombination in semiconductors and the sluggish kinetics of conventional Fenton-like processes. The development of efficient heterojunction photocatalysts with accelerated Fe 3+ /Fe 2+ cycling is crucial for advancing photo-Fenton oxidation in wastewater treatment. In this work, layered TiO 2 /MIL-100(Fe) heterojunctions were prepared by a one-step in-situ solvothermal approach. When tested with H 2 O 2 under visible light, the optimal composite (HF-2) removed 93.2% of Methyl Blue (MB) over a 60-min reaction period. The derived pseudo-first-order kinetic constant (0.028 min −1 ) exhibits a 2.0-fold increase relative to TiO 2 and a 1.4-fold rise compared with pure MIL-100(Fe). Structural and band-alignment analyses corroborate the establishment of a tightly coupled Type-II heterojunction at the TiO 2 /MIL-100(Fe) heterointerface. This architecture promotes directional electron transfer from TiO 2 to MIL-100(Fe), thereby accelerating the Fe 3+ /Fe 2+ redox cycle. Notably, radical quenching and electron paramagnetic resonance (EPR) analyses reveal that MB degradation proceeds predominantly via a non-radical pathway dominated by singlet oxygen ( 1 O 2 ), distinguishing this system from conventional ·OH-centric Fenton processes. Furthermore, the composite displays outstanding structural stability and recyclability, maintaining 90% of the original catalytic performance upon five repeated cycling tests. The present study puts forward a reasonable design route to develop high-efficiency heterojunction photocatalysts, and also delivers new understandings on the non-radical photo-Fenton pathway for the treatment of dye-containing wastewater.