Flame-retardant nanocoating towards high-efficiency suppression of smoke and toxic gases for polymer foam

•An eco-friendly flame-retardant porous nanocoating has been developed for flexible polyurethane foam.•The nanocoating shows the high efficiency of flame retardancy and suppression of smoke and toxic gases.•The nanocoating has a little negative effect on the mechanical properties of the foam.•The flame-retardant and smoke-suppression mechanism of the nanocoating has been revealed in detail.