Catalytic membranes with integrated pore-confinement of ultrasmall noble metal nanoparticles: Realizing pollutant degradation in complex water matrices

Catalytic membranes with leaching-resistant noble metals offer promise for continuous oxidative water purification, but their adoption is hampered by inefficient catalyst utilization and poorly understood reaction mechanisms. Here, we present the in situ synthesis of entangled particle-polymer complexes within the casting solution to fabricate polyethersulfone membranes with pore-confined ultrasmall noble metal nanoparticles. This all-in-one approach maximizes catalyst utilization by achieving pore surface confinement of nanoparticles in near-quantitative yields. By combining thermodynamic, kinetic, and radical probe analyses, we reveal the catalytic mechanisms of pore-confined Ag, Au, Ru, and Pd in degrading ofloxacin via peroxymonosulfate (PMS) activation in a realistic water matrix. We further introduce a novel mechanistic model for catalytic pollutant remediation in complex environments, providing a fundamental advance for rational catalyst design. Going beyond conventional models, our model integrates several key catalyst parameters into a single quantitative rate equation: thermodynamic reactivity of active species, catalytic rate constant, PMS affinity, and interference by water matrix components. Furthermore, a unique dual radical/non-radical PMS activation pathway was identified for pore-confined Pd, promoting a catalytic turnover frequency an order of magnitude higher than those of catalytic membranes reported in the literature. The Pd-decorated membrane also drastically outperformed comparable systems for continuous water treatment under environmentally-relevant conditions: it achieved complete flow-through degradation (1.2 s residence time) of 10 μg L −1 ofloxacin in an ionic matrix at neutral pH to below the predicted no-effect concentration (<26 ng L −1 ), maintaining this single-pass removal over 80 h (28 000 L m −2 volume) flow operation without any metal leaching. • Porous polymer membranes with pore-confined ultrasmall Ag, Au, Ru, Pd nanoparticles. • Novel threshold-gated Eley-Rideal mechanism for catalytic pollutant degradation. • Synergistic dual radical and non-radical peroxymonosulfate activation pathway. • Flow-through rate constant of 796 s −1 m −2 and turnover frequency of 1225 μg mg −1 h −1 . • Complete ofloxacin removal at 1.2 s residence time in realistic ionic water matrix.