Hierarchical porous melamine sponge@MIL-101-Fe-NH₂ composite as Fenton-like catalyst for efficient and rapid tetracycline hydrochloride removal

Metal-organic frameworks have been investigated in Fenton-like catalysis for tetracycline hydrochloride degradation, a widely used antibiotic which threatens the growth and health of creatures. However, powder phase and absence of large pores limit the materials' degradation performance and application. In this work, a hierarchical macro-meso-microporous composite melamine sponge@MIL-101-Fe-NH₂ was firstly designed and constructed. While the micropores provided plenty of active sites to generate reactive oxygen species, the macropores and mesopores accelerated mass transfer. Besides, MIL-101-Fe-NH₂ particles dispersed on melamine sponge individually, exposing more catalytic sites and avoiding inactivation caused by aggregation compared to powder catalysts. Its catalysis performance for tetracycline hydrochloride degradation was evaluated through changing various influence factors like H₂O₂ concentration, catalyst amount, pH and coexisting ions. Different from the preference of homogenous Fenton catalysts for pH 2-4, the composite displayed the most effective degradation at a subacid environment closer to nature with 77.24% in 30 min. Owing to the synergistic effect of hierarchical porous structure and monodispersed nanoparticles, the composite exhibited faster reaction rate and longer persistence compared to powder MIL-101-Fe-NH₂. Easy recycling and less ion leaching made it advantages for practical application. •OH, •O₂^- and ¹O₂ active species contributed together to the degradation and two main possible degradation pathways were put forward based on 35 detected intermediates.