Fe-based metal-organic frameworks as Fenton-like catalysts for highly efficient degradation of tetracycline hydrochloride over a wide pH range: Acceleration of Fe(II)/ Fe(III) cycle under visible light irradiation

In this work, a series of Fe-based metal-organic frameworks (Fe-MOFs) were synthesized and served as Fenton-like catalysts for tetracycline hydrochloride (TC–HCl) degradation. Herein, for the first time, we have demonstrated that visible light can accelerate Fe(II)/Fe(III) cycle in the photo-Fenton system based on iron-oxo (Fe-O) clusters in frameworks. Among these Fe-MOFs, MIL-101 possessed the highest activity mainly ascribed to its largest specific surface area and pore volume, and the most coordinatively unsaturated iron sites. The synergistic effect in the MIL-101/H 2 O 2 /visible light system was derived from the efficient separation and migration of photogenerated carriers. Due to the function of solid acid catalysts, MIL-101 extended effective pH range up to 10.2 and exhibited good reusability and stability. Hydroxyl radicals generated from H 2 O 2 coordinated at iron active sites were determined as the main reactive oxidative species and acceleration of Fe(II)/Fe(III) cycle was responsible for highly effective degradation of TC–HCl.