Amino-functionalized MIL-88B as heterogeneous photo-Fenton catalysts for enhancing tris-(2-chloroisopropyl) phosphate (TCPP) degradation: Dual excitation pathways accelerate the conversion of FeIII to FeII under visible light irradiation

In this work, the amino-functionalized metal-organic frameworks (MIL-88B-NH 2 ) was synthesized, characterized and used as heterogeneous photo-Fenton catalyst for tris-(2-chloroisopropyl) phosphate (TCPP) degradation. The photo-Fenton activity of MIL-88B-NH 2 was investigated on the basis of influence factors, such as initial pH and TCPP concentration, and coexisting impurities. The results revealed that MIL-88B-NH 2 +H 2 O 2 +Vis system exhibited a satisfactory degradation efficiency of TCPP (almost 100%) within 60 min accompanied by a good reusability. Noticeably, the degradation kinetics constant of TCPP by MIL-88B-NH 2 +H 2 O 2 +Vis system was 0.086 min −1 , which was visibly higher than that of MIL-88B+H 2 O 2 +Vis system (0.021 min −1 ) since the addition of amino-functionalized organic linker inhibiting the recombination rate of the photo-generated electron-hole pairs and improving the visible light response. Combined with the characterization, the conversion of Fe III to Fe II could be accelerated by the photo-generated electron from the excitation of Fe-O clusters and NH 2 functionalities, which strengthened the decomposition of H 2 O 2 and formed plenty •OH. Simultaneously, six steady products were validated and potential degradation pathways of TCPP were proposed. It was anticipated that MIL-88B-NH 2 could be considered as a desirable and alternative candidate in the application of heterogeneous photo-Fenton reaction to control the environmental risks caused by organophosphate flame retardants (OPFRs).