An inorganic–organic silica material (SBA–P2), prepared by immobilization of the 1,8-naphthalimide-based receptor P2 within the channels of the mesoporous silica material SBA-15, is characterized by transmission electron microscopy and several spectroscopic methods. SBA–P2 features a high affinity Cu2+-specific fluorescence response in aqueous solution with a detection limit for Cu2+ of ca. 0.65 ppb (10 × 10−9 M) under optimized conditions. It can extract Cu2+ from the solution with only trace amounts remaining. Through isolating of the toxic ions within the mesopores of the silica, SBA–P2 has the potential to work as a toxicide for Cu2+ in living systems. The fluorogenical responses are reversible and do not vary over a broad (4.0 to 9.0) pH range suitable for application under physiological conditions. The fluorescence responses of Cu2+ in vitro (human breast cancer cells) and in vivo (five-day-old zebrafish) demonstrate the possibility of further application in biology.