Aluminium-magadiite: from crystallization studies to a multifunctional material

Abstract

The synthesis of [Al]-magadiite (Si/Al = 15) was monitored during preparation and crystallization by the Aluminium-Induced Crystallization method developed previously (G. B. Superti, E. C. Oliveira, H. O. Pastore, G. Gatti and L. Marchese, Chem. Mater., 2007, 19, 4300–4315.). For monitoring purposes samples were collected at 0, 12 and 24 h and after aluminium introduction at 0, 6 and 12 h of hydrothermal treatment. A systematic study of the physicochemical and thermal properties of the products obtained at each step in [Al]-magadiite synthesis was performed by combining different experimental techniques [infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA) and solid-state magic-angle spinning nuclear magnetic resonance (MAS-NMR)]. ²⁷Al MAS NMR confirmed the insertion of Al ions into the magadiite framework in tetrahedral positions. The results obtained showed that the hydrothermal treatment before aluminium insertion served essentially for the creation of magadiite seeds. Thus, induced crystallization by introduction of magadiite seeds directly in the synthesis gel showed that the synthesis duration could be reduced and variable Si/Al ratios showed that the increase in aluminium concentration affects the crystallinity of the material and allows us to obtain [Al]-magadiite with different Si/Al ratios in a single step. Different Al_td nonequivalent sites were detected by 3QMAS-NMR experiment. X-Ray photoelectron spectroscopy (XPS) allowed designing the [Al]-magadiite structure as a pure silicon magadiite core with a thin layer of aluminosilicate deposited on top of it.