LDH-Enhanced Degradation of PFASs: Influence of Reactant Configurations within Nanoconfined Spaces on Hydrated Electron Transport

Hydrated electron (e aq – ) reduction is an efficient pathway for degrading per- and polyfluoroalkyl substances (PFASs). Nanoconfined spaces can shield e aq – from quenchers in bulk solution and shorten diffusion distances, thereby enhancing utilization efficiency. However, the role of e aq – precursors and PFASs configurations within nanoconfined domains in governing e aq – transport remains unclear. In this study, polyindole (Pind) was synthesized within layered double hydroxide (LDH) interlayers as an e aq – precursor, while perfluorooctanoic acid (PFOA) was simultaneously enriched through electrostatic interaction. Although the e aq – yield increased with Pind loading, the PFOA degradation rate followed a unimodal trend, reaching a maximum at 27.2% Pind loading, where complete degradation was achieved within 3 h. Molecular dynamics simulations revealed stronger hydrophobic interactions among Pind molecules than between Pind and PFOA, leading to a configuration where PFOA surrounded Pind aggregates. With increasing Pind loading, this arrangement forced more e aq – to travel longer distances to attack C–F bonds, reducing their utilization efficiency despite higher overall yields. This “yield-transport” self-antagonism underscores the critical role of nanoconfined configurations in e aq – transport and utilization efficiency and provides mechanistic insights for the rational design and optimization of nanoconfinement systems.