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/H2O2/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 H2O2 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.