Design of silicate nanostructures by interlayer alkoxysilylation of layered silicates (magadiite and kenyaite) and subsequent hydrolysis of alkoxy groups

Abstract

Silica nanostructures are sophisticatedly designed by interlayer alkoxysilylation of layered silicates (magadiite and kenyaite) with alkoxytrichlorosilanes and the subsequent hydrolysis of alkoxy groups. The dichlorosilyl groups of alkoxytrichlorosilanes [(RO)ClSiCl₂] were reacted onto two neighboring Si–OH groups on the surface of the layered silicates to form a bridge, leaving two functional (Si–OR and Si–Cl) groups on the bridge. The remaining bifunctional groups were almost completely hydrolyzed to transform into Si–OH groups. Depending on the solvent for hydrolysis, the hydrolyzed product derived from magadiite forms either a new 3-D silicate structure by condensation of interlayer silanol groups or a new 2-D silicate structure by geminal Si–OH groups remaining immobilized on both sides of the silicate layers. The 3-D silicate structure exhibits microporosity (130 m² g⁻¹) and hydrophilic behavior. On the other hand, the hydrolyzed product from kenyaite takes only a 2-D silicate structure, even when the solvents for hydrolysis were completely evaporated.