Synthesis and characterization of germanium, copper- and cobalt-substituted ITH-zeotype materials

ITH-type germanosilicate, Cu- and Co-containing ITH-zeotype materials, were synthesized by the hydrothermal method in the presence of an organic structure-directing agent, N,N,N′,N′-tetramethyl-1,6-hexanediamine. The effects of reaction compositions, including the molar ratios of SiO2/GeO2, SiO2/H2O, and MeO/SiO2 (Me = Cu and Co transition atoms) on the synthesis of the pure product were investigated. The synthesized samples were characterized by powder and single-crystal X-ray diffractions, scanning electron microscopy, inductively coupled plasma (ICP) analysis, energy dispersive spectrometry, thermogravimetric analysis, UV–Vis diffuse reflectance spectrum (DRS) measurements, X-ray photoelectron spectroscopy, and N2 adsorption and desorption analysis. The results reveal that the concentration of H2O in the reaction mixture has an important impact on the synthesis of pure ITH-type zeolite. The framework’s Si/Ge ratio is slightly changed from 3.1 to 3.9 when the initial SiO2/GeO2 molar ratio is increased from 0.8 to 10. Structure refinement results show that the Ge atoms preferably occupy sites in the double-four ring units. Cu and Co atoms have been introduced for the first time into ITH-type materials. The trace amounts of amorphous Cu- and Co-compounds in the resulting materials can be readily detected by backscattered electron imaging, so that pure samples can be selected for ICP and UV–Vis DRS measurements.