Chelation-based metal cation stabilization of graphene oxide membranes towards efficient sieving of mono/divalent ions

Mono/divalent ions separation is an extremely crucial yet difficult task. Two-dimensional (2D) graphene oxide (GO) membranes with exquisite interlayer nanochannels are promising to discriminate mono/divalent ions, but they suffer from serious swelling issue. Inspired by biological metal cation immobilization paradigm, we propose a universal chelation-based metal cation stabilization strategy of GO membranes. The chelation of polydentate ligand with metal cation generates thermodynamically stable coordination complexes to sustain GO interlayer via multiple binding forces. By synergism of firmly immobilized metal cations controlling 2D nanochannels against swelling to ensure divalent ions retention, and rationally incorporated polydentate ligands decorating 2D nanochannels with hydrophilic groups to facilitate monovalent ions permeation, the as-fabricated GO/ligand-M2+ membranes afforded superior sieving performance of monovalent ions permeance of ∼0.78 mol m−2 h−1 and mono/divalent ions selectivity of ∼23.5. This work provides a general design concept for the stabilization of 2D laminar membranes towards efficient sieving of mono/divalent ions.