A novel Fe-based bi-MOFs material for photocatalytic degradation of tetracycline: Performance, mechanism and toxicity assessment

Metal-organic frameworks (MOFs) are new porous materials that attract wide attention due to their environmentally-friendly photocatalytic characteristics. However, poor charge separation in most MOFs largely limits their photocatalytic activity. In this study, a novel Fe-based bi-MOFs heterojunctions material, namely NH2-MIL-88B(Fe)@MIL-100(Fe) was prepared by internal extended growth of MIL-100(Fe) on spindle-like NH2-MIL-88B(Fe). Compared with pure NH2-MIL-88B(Fe) and MIL-100(Fe), the synthesized Fe-based bi-MOFs structure catalyst displayed excellent photocatalytic degradation of tetracycline (TC), with optimal removal of 99.9% achieved in 90 min under neutral conditions. This result is attributed to the sufficient visible light absorption, and the enhanced separation and transfer of h+ and e− by the bi-MOFs structure. In particular, ∙O2−, h+ and ∙OH showed synergistic effects in the photodegradation process, and Fe-based bi-MOFs displayed high stability after five cycles. The inhibition ratio of luminescent bacteria of the degraded solution was lower than 24%, indicating the high efficiency and safety of this Fe-based bi-MOFs for the treatment of antibiotic-contaminated water.