Direct Synthesis of Functionalized Mesoporous Silica by Non-Ionic Assembly Routes. Quantitative Chemical Transformations within the Materials Leading to Strongly Chelated Transition Metal Ions

Abstract

This paper describes a general way permitting the quantitative introduction of strongly chelated transition metal ions. For that purpose, the direct synthesis of mesoporous silica containing chloropropyl groups has been achieved by using three different nonionic surfactants (n-hexadecylamine, tergitol 15-S-12, and the triblock copolymer P123) as structure-directing agents. Substitution of chloropropyl groups located within the pores by cyclam was then investigated; cyclam (1,4,8,11-tetraazacyclotetradecane) is well-known for its remarkable binding ability toward transition metal salts. We showed that the substitution of chloro groups by the cyclam depends on the mean pore size of the material. Anchoring of the cyclam moieties occurred almost quantitatively within the materials prepared in the presence of the triblock copolymer P123 and that without modification of the mesostructure. The binding ability of the cyclam toward transition metals salts was tested with CoCl2 and CuCl2. It was found to be maintained within the materials. All the cyclam moieties located within the pores' channels are accessible, leading to materials containing strongly chelated transition metal ions.