Photofunctional Silica Gel Beads as Environmental Conscious Materials

Abstract

Photofunctional silica gel beads have been developed as environmental conscious materials. The hydroxybenzophenone (Hbp) chromophore–bonded silica gel (SiO₂) beads (1) were developed as UV–absorbents. 4,5–Dimethoxy–2–nitrobenzyloxycarbonyl (Nbz) chromophore–bonded SiO₂ (2) was prepared in order to control the amounts and sites of functional group by a use of Nbz as a photolabile protecting group. Diacetoxyantimony tetraphenylporphyrinato chromophore (Sb(OAc)₂tpp)–bonded SiO₂ (3a) was packed in micro–channel reactor. The photoreaction of 3a with Et₂NH induced the demetallation to give free base tetraphenylporphyrin chromophore (H₂tpp)–bonded SiO₂ (3b). The color change of the H₂tpp–H–adsorbed SiO₂ (4) under dry and humidity conditions was applied to a new type of humidity indicator without CoCl₂. The Sb(OH)₂tpp–H–adsorbed SiO₂ (5) was used as visible light driven photocatalysts in dechlorination of 4–chlororophenol, epoxidation of cyclohexene, and bactericidal reaction of E. coli. Also dimethoxophosphorus tetraphenylporphyrine (P(OMe)₂tpp–H)–adsorbed SiO₂ (6b) was practically used to sterilization Legionella species naturally occurring in fountain.