Regulating defect density of iron based metal-organic frameworks by defective ligands functionalization to enhance fenton-like activity and stability

Generating defect sites in iron based metal-organic frameworks (Fe-MOFs) by introducing defective ligands has recently emerged as an effective approach to optimize Fenton-like activity, but the structure-activity relationship between defective ligands and Fenton-like reaction is still not fully understood. Herein, a series of defective MIL100(Fe), i.e., Dx-MIL-100(Fe), were constructed via introducing defective ligands with various functional groups including -N,-NO2,-Cl and -OH. It was observed that defect density and Fenton-like activity of DX-MIL-100(Fe) is positively correlated with the electronegativity of functional groups in defective ligands. With the increasing defect density, the stability and recyclability of DX-MIL-100(Fe) in Fenton-like reaction was not decreased, which is attributed to increasing coordination bond energy between defective ligands and Fe-O cluster. The high defect density results in the increase of electron density of Fe and rate of FeIII reduction. Therefore, DN-MIL-100(Fe) possessing highest defect density exhibited superior Fenton-like activity with the pseudo-first-order kinetic constant up to 0.089 min(-1) for Bisphenol A degradation, which is 148.3 times than that of perfect MIL-100(Fe). Meanwhile, DN-MIL-100(Fe) showed excellent pH adaptability, anti-interference ability and cycle stability. This work unravels the role of functional groups in defective ligands on regulating defect density, Fenton-like activity and stability for the first time, which can provide a novel platform for precisely designing Fe-MOFs as promising Fenton-like catalyst.