Preparation of ordered SBA-15 mesoporous silica containing chelating groups. Study of the complexation of Eu-III inside the pore channels of the materials

Ordered mesoporous silica containing 3-chloropropyl groups was prepared by a direct synthetic approach involving hydrolysis and co-condensation of tetraethylorthosilicate (TEOS) and 3-chloropropyltrimethoxysilane in the presence of the triblock copolymer P123 as the structure-directing agent and under acidic conditions. Nucleophilic displacement of chloro groups by cyclam moieties (cyclam=1,4,8,11-tetraazacyclotetradecane) was then achieved almost quantitatively. Subsequent treatment of solids containing different amounts of cyclam moieties with an ethanolic solution of europium (III) chloride gave rise to 1:1 Eu-III/cyclam complexes. The EXAFS studies have shown that Eu-III adopts an octahedral geometry.