Bioinspired cascade‑functional hydrogel membranes with electrostatically assembled heterogeneous domains for...

Efficient capture of U(VI) hinges not solely on high coordination-group density, but critically on the concerted regulation of site accessibility, ion partitioning, and network hydration. Drawing inspiration from the functional specialization and cooperative interplay of heterogeneous units in biological immune responses, we develop an electrostatically assisted precursor-assembly strategy to construct a ternary poly(acrylic acid)-poly(amidoxime)-poly(styrenesulfonic acid) (PAA-PAO-PSS) hydrogel membrane with differentiated yet synergistic functional domains. Gradual PSS addition into PAO dispersion suppresses excessive local complexation and aggregation, yielding a homogeneous precursor. PSS-enriched domains regulate hydration, the negative microenvironment, and ion competition, while PAO domains provide high-affinity N/O sites, establishing a cascade process of ion pre-screening, hydrated transport, and coordination anchoring within a crosslinked PAA network. The representative PSS60% membrane achieves a Langmuir capacity of 609 mg g⁻¹ and retains 89.1% capacity after five cycles, with favorable ion selectivity. Spectroscopic, XAFS, and DFT analyzes confirm that PSS modulates hydration and partitioning, PAA carboxyl groups assist, and PAO amidoximes chelate U(VI). This work establishes precursor-pathway engineering as an effective strategy for constructing heterogeneous adsorption microenvironments and provides a general design principle for high-performance radionuclide adsorbents.