Dual-Redox-Enabled Photocatalytic Degradation of PFOA over a MIL-125-NH2/rGO Composite

Abstract

The degradation of perfluorooctanoic acid (PFOA) remained challenging due to the extraordinary stability of its carbon–fluorine bonds, which were resistant to conventional photocatalytic processes. In this work, a metal–organic framework (MOF), MIL-125-NH2, was grown in situ on reduced graphene oxide (rGO) to form nanocomposites (RMGs), enabling rapid PFOA degradation via an integrated dual-redox pathway without the addition of sacrificial agents. Under UV irradiation, the RMG composite achieved an 80.2% degradation of PFOA (20 mg L–1) within 4 h, corresponding to an apparent rate constant of 0.405 h–1, and exhibited competitive degradation productivity among reported photocatalytic systems operating without external oxidants or sacrificial agents. PFOA degradation exhibited pronounced pH dependence with the RMG composite delivering optimal performance at pH 5. Moreover, the RMG catalyst showed excellent stability and reusability. In natural water matrices, the RMG composite achieved approximately 70% PFOA degradation within 10 h. The MOF/rGO heterojunction promoted directional charge separation, enabling photogenerated holes to trigger carbon–carbon bond cleavage and stepwise shortening of perfluorinated intermediates, while electrons were efficiently transferred to PFOA to induce hydrogen–fluorine atom exchange. Overall, this study highlights the pivotal role of synergistic redox integration in enabling efficient PFOA remediation in aqueous systems.