Enhanced photocatalytic defluorination of perfluorooctanoic acid through integrated hydrogen atoms/electrons reduction and ROS oxidation with metal–organic framework heterogeneous catalysts

Abstract

The escalating prevalence of perfluorooctanoic acid (PFOA) abuse and discharge globally poses a substantial threat to human health and aquatic ecosystems. However, the removal of persistent PFOA from water sources remains a challenge. Herein, Fe-BTC/BiOCl, a bifunctional photocatalyst combining iron-based metal–organic framework (MOF) and bismuth oxychloride, was developed that integrated the hydrogen atoms/electrons reduction with reactive oxygen species (ROS) oxidation to facilitate an efficient photocatalytic process aimed at the deep defluorination and mineralization of PFOA. Considering the 3D nanostructures, strong electronic interaction and interlaced energy band structure, a Z-scheme Fe-BTC/BiOCl heterostructure was fabricated to attain efficient carrier separation accompanied by a significant abundance of oxygen vacancies. Under LED-lamp irradiation, the Fe-BTC/BiOCl heterostructure obtained 98.7 % degradation of PFOA within 30 min. Electron paramagnetic resonance analysis and scavenging experiments indicated that the ROS and hydrogen atoms/electrons generated in the Fe-BTC/BiOCl/visible light system were the primary active species responsible for the efficient degradation of PFOA. Furthermore, the quantitative analyses of intermediates and density functional theory calculations revealed that the PFOA degradation process primarily involve the prioritized cleavage of carboxyl group and the subsequent repeated unzipping cycle that included the removal of − CF₂H groups and elimination of fluoride ions due to the cleavage of C–C and C − F bonds, respectively. These findings offer precious insights for designing green and efficient photocatalysts and enhance understanding of the photocatalytic defluorination processes for PFOA.