One-step synthesis, characterisation and properties of core/shell silicogermanate zeotype crystals

摘要

The core/shell composite silicogermanate zeotype material, Si-ASU-7, has been prepared in a one-step solvothermal synthesis process from a reactant mixture of GeO2 and SiO2 in a dimethylamine/H2O/HF solvent mixture. The core/shell nature of the product material has been determined using a combination of X-ray diffraction on powder and single crystal samples, and energy dispersive X-ray spectroscopy. The crystal structure of Si-ASU-7, ([Si_(0.221)Ge_(0.779)O2]_(10)·(Me2NH)(H2O), tetragonal, space group P4/ mnc, a = 12.3484(3) k, c = 14.3979(5) A, V= 2195.43(11) A~3) determined using single crystal X-ray diffraction data indicates that incorporation of silicon into the structure introduces a degree of disorder to the orientation of the double 4-ring secondary building units from which the framework is constructed. The thermal stability of the as-synthesised composite Si-ASU-7 material is enhanced compared to the pure germanate material ASU-7.