Investigation of the structure of MCM-41 samples with a high copper content

A series of MCM-41S with a high, copper content were synthesized at room temperature from sodium metasilicate (Na₂SiO₃) as the silicon source, tetraamminecopper(II) nitrate [Cu(NH₃) ₄(NO₃)₂] as the copper source and cetyltrimethylammonium bromide (CTABr) as the template; The resulting material was characterized by using the following characterization techniques: X-ray diffraction (XRD), N₂-adsorption isotherms, high-resolution transmission electron microscopy (HRTEM), inductively coupled plasma (ICP), temperature-programmed reduction (H₂-TPR), X-ray photoelectron spectroscopy (XPS), Fourier-trans-form infrared spectroscopy (FTIR), UV-vis spectroscopy, electron-spin resonance (ESR) and ²⁹Si magic-angle sample spinning nuclear magnetic resonance (MAS NMR) spectroscopy. The characterization techniques demonstrated the following: i) the copper atoms are incorporated into the framework of MCM-41 and ii) the copper species in the samples are in a distorted octahedral coordination environment, with between four and six oxygen atoms in the first coordination sphere. The maximum copper content determined by ICP was 26 wt.-% in the ordered mesoporous sample with a surface area of 525 m² g^-1 and an average pore diameter of 3.1 nm. The synthesized materials exhibited a high activity for nitrogen monoxide (NO) reduction by carbon monoxide, (CO).