Controlled Ion Dehydration-Driven Catalysis Enabled by Reverse-Mode Nanofiltration

Abstract

Catalysis under nanoscale confinement is widely pursued, but practical systems remain limited by a persistent contradiction: maximizing confinement-enhanced reactivity usually increases the residence time and accelerates pore failure. Here we present a ceramic nanofiltration platform that resolves this trade-off by coupling subnanometer confinement with transient, flow-through ion dehydration. The membrane is constructed by atomic layer deposition on a hierarchical α-Al2O3/γ-Al2O3 scaffold, yielding a robust, ultrathin Al2O3 active layer with tunable nanochannels and minimized transport distance to the reaction interface. During transmembrane permeation, Fe2+ ions are partially dehydrated, exposing vacant coordination sites that immediately react with H2O2 upon emergence to degrade organic micropollutants (e.g., tetracycline). This synergistic process yields a kinetic enhancement ratio of 90.5% for the dehydration group relative to the corresponding rehydration group. The kinetic enhancement ratio obtained with the commercial polyamide nanofiltration membrane NF270 under the same comparison framework was substantially lower. Beyond activity, the inorganic architecture sustains 30 d of continuous backwashing with <3% fluctuation in pure-water permeability and exhibits a kinetic enhancement ratio of 89.6% after backwashing. Importantly, the reverse-mode configuration reduces reliance on prolonged reactant residence within nanopores, thereby lowering the risk of pore blockage. These results establish a membrane-enabled strategy for capturing nonequilibrium ionic states and thereby translate nanoconfinement chemistry into an operationally durable format, with broad implications for water treatment, electrochemical conversion, and selective resource recovery.