▎ 摘　　要

NOVELTY - Preparing a metal ion cross-linked nano-film comprises (1) preparing hydrogel, and swelling the prepared hydrogel to saturation in water, (2) soaking the swollen hydrogel to saturation in the aqueous solution of metal ions for a given time, and removing out, (3) immediately and continuously adding the spreading solution to the surface of the freshly removed hydrogel, where the spreading solution super spreads on the surface of the wet hydrogel, carrying out the interfacial film-forming reaction, completing the reaction, and obtaining nano-film on the surface of the hydrogel, and (4) transferring the nanomembrane to any solid surface, washing to remove excess metal ions, drying, and peeling off from the solid surface to obtain metal ion crosslinked nanomembrane. USE - The method is useful for preparing a metal ion cross-linked nano-film, which is useful in the fields of water treatment, ion/molecule separation, battery, capacitor, and confinement reaction (claimed). ADVANTAGE - The metal ion cross-linked nano-membrane has high stability, high degree of orientation, precise and controllable interlayer distance reaching Angstrom level, and has no obvious swelling in water, and consistent interlayer distance in the air. DETAILED DESCRIPTION - An INDEPENDENT CLAIM is also included for metal ion cross-linked nano-film.