A dual-functional organic-inorganic film with gas barrier and hydroxide ion conductivity properties was fabricated via the layer-by-layer assembly of layered double hydroxide (LDH) nanoplates and quaternary ammonium grafted polysulfone (QAPSF). By incorporating inorganic flakes with high ionic conductivity and gas barrier effects into an ion-conductive polymer matrix, this work overcomes the commonly-believed incompatibility between gas blocking and ionic conduction.