Photocatalytic activation of peroxodisulfate using iron-containing MOFs synthesized by single-crystal-to-single-crystal transformation for ofloxacin degradation

Abstract

Iron-containing metal–organic frameworks (Fe-MOFs) are promising photocatalysts for the activation of peroxysulphate. In this work, a new robust MOF (Fe₂In-TCA) was successfully prepared through single-crystal-to-single-crystal (SC–SC) transformation using an indium-MOF template (In₃-TCA) (TCA = 4,4′,4′′-nitrilotribenzoic acid). The SC–SC transformation led to the obtention of large-sized Fe₂In-TCA crystals suitable for single-crystal X-ray diffraction. More fascinatingly, compared to the sample (Fe₂In-TCA-D) synthesized by the one-pot in situ method, Fe₂In-TCA not only showed a higher specific surface area but also showed better charge separation and migration efficiency, indicating that postsynthetic metal metathesis is an advanced strategy for preparing Fe-MOFs. With these advantages, Fe₂In-TCA exhibited enhanced photocatalytic activity for activating peroxydisulfate (PDS). Under optimum conditions, Fe₂In-TCA removed about 98% of ofloxacin (OFL) in 30 minutes and could be reused over five cycles. Further mechanism studies showed that free radicals (˙SO₄⁻, ˙OH, O₂˙⁻), singlet oxygen (¹O₂), and photogenerated holes (h⁺) were the main active species for OFL degradation. These results show that Fe₂In-TCA can be used as a potential photocatalyst to activate PDS to degrade OFL. This work provides a new perspective for the construction of robust Fe-MOFs for photocatalytic OFL degradation.