Versatile and robust poly(ionic liquid) coatings with intelligent superhydrophilicity/superhydrophobicity switch in high-efficient oil-water separation

•Versatile methods are applied on different substrates to fabricate intelligent materials for oil-water separation.•The PCMs exhibited switchable superhydrophilic/superhydrophobic properties.•The PCMs could switch the separation performances between “oil-removing” and “water removing” by anion exchange.•The PCMs would meet different requirements in oil-water separations: fast separation, ultra-efficient separation, water/oil adsorption and recycle.