Programming Ion Transport in Layered 2D Hybrid Membranes via Coordination-Occupation Coupling

The sustainable separation of chemically distinct yet notoriously difficult-to-separate metal ions is a critical challenge for nuclear waste management and strategic resource recovery. Layered two-dimensional (2D) membranes offer energy-efficient alternatives to conventional extraction and adsorption technologies, yet their selectivity is often constrained by fixed and poorly tunable transport pathways. Here we introduce a coordination-occupation-coupled strategy to program ion transport in layered 2D hybrid membranes combining a confined polyacrylate network between layered vermiculite. Irreversible crosslinking with Al³⁺ ions within polyacrylate network forms unexchangeable coordination sites that stabilize the membrane structure and selectively occupy transport pathways for multivalent ions. This targeted pathway occupation suppresses the transport of Sr²⁺, La³⁺ and Zr⁴⁺, while allowing Cs⁺ to permeate efficiently through alternative routes. The resulting membranes achieve Cs⁺/Sr²⁺ separation factors approaching 10³ and near-complete separation of Cs⁺ from trivalent and tetravalent ions. This work establishes coordination-occupation coupling as a scalable and material-efficient principle for high-selectivity ion separations, with direct implications for sustainable radionuclide remediation and critical metal recovery.