Insights into highly efficient photodegradation of poly/perfluoroalkyl substances by In-MOF/BiOF heterojunctions: Built-in electric field and strong surface adsorption

Poly/perfluoroalkyl substances (PFASs) are ubiquitous organic pollutants and the strong C-F bonds make them recalcitrant for degradation. In this study, novel In-MOF/BiOF heterojunctions at different doping ratios were synthesized, characterized and evaluated for the photocatalytic removal performance on Perfluorooctanonate (PFOA), perfluorooctane sulfonate (PFOS), hexafluoropropylene oxide trimer acid (HFPO-TA) and 6:2 chlori-nated polyfluorinated ether sulfonate (6:2 Cl-PFESA). 20% In-MOF/BiOF exhibited effective and complete degradation of PFOA (15 mg/L) under illumination. The reaction rate constants decreased in the order of PFOS > 6:2 Cl-PFESA > PFOA > HFPO-TA. The density functional theory calculation revealed that the reaction rate constant positively correlated with adsorption energies of the PFASs on the catalyst. Additionally, the generation of built-in electric field at the In-MOF and BiOF interfaces enhanced the efficient separation of photogenerated carriers, thus intrinsically facilitated the catalytic performance. The study sheds light on the construction of built-in electric field to improve photocatalytic performance.