Hydrothermal synthesis and characterization of copper containing crystalline silicate mesoporous materials from gel mixture

Novel copper-containing crystalline silicate mesoporous materials (SCMM) have been synthesized by the hydrothermal treatment of slurries of silicon–magnesium–copper hydroxide precipitates along with quaternary ammonium salt. X-ray diffraction (XRD) and transmission electron microscopy (TEM) confirmed a house-of-cards type structure consists of very thin platy silicates. Nitrogen adsorption–desorption isotherms of calcined material show that it has a high surface area (∼550 m2 g−1) and porosity properties. Pore characteristics are similar to that of MCM-41 and FSM-16, and fine-tuning of the pore size was achieved easily by modulating the synthesis temperature. Identification and the location of copper species in Cu-SCMM were done by X-ray photoelectron spectroscopy (XPS) and electron spin resonance (ESR), respectively. ESR data of air-dried Cu-SCMM consist of clearly defined g||=2.34, A||=140×10−4 cm−1 and g⊥=2.08 at room temperature and g||=2.34, A||=160×10−4 cm−1 and g⊥=2.10 at 77 K. The resulting material exhibited superior catalytic activity towards the hydrogenation of α–β unsaturated aldehyde in supercritical carbon dioxide.