Polyurethane network 1 was prepared through curing of epoxy-based polymer bearing 1-naphthylamine units with tolylene-2,4-diisocyanate as curing agent. With ferric ions, the network was found to exhibit selective ON-OFF-type fluorescence signaling behavior even in the presence of other representative metal ions such as Na+, K+, Ag+, Cu2+, Zn2+, Co2+, Ni2+, Cd2+, Hg2+, Mg2+, Sr2+, Pb2+ and Ca2+ ions.