The Synthesis Of Copper Silicates And Strontium Silicates With Microporous Mixed Octahedral-Pentahedral-Tetrahedral Framework

The OPT silicates are a new class of stable microporous materials that have novel mixed octahedral-pentahedral-tetrahedral (OPT) frameworks. As their new topologies and novel compositions, these materials not only have potential novel applications in the fields normally associated with zeolites but also possible applications in the areas of optoelectronics, nonlinear optics, batteries, magnetic materials and sensors.Herein, the study is about several copper silicates and strontium silicates with OPT frameworks. The detailed synthesis conditions and mechanisms have been systematically investigated, and the typical samples have been characterized by XRD, SEM, TG and optical microscope analysis. The main contents and results are listed as follows:Firstly, pure-phase copper silicate AV-23 (Na2Cu2Si4O11·2H2O) was hydrothermal synthesized from NH3-Na2O-Cu(NO3)2-SiO2-H2O system. To avoid the formation of polycrystalline CuO, aqueous ammonia was used as complexing agent. The best adding sequence of raw chemicals is distilled water, copper nitrate trihydrate, ammonia solution, sodium hydroxide, and silica sol. The ICP, XRD and SEM measurements of the precursors indicated this sequence can effectively adjusts the precipitation-complexing-competition and alkali competition balance in the solution and made copper present in the form of both Cu(OH)2 and [Cu(NH3)4]2+, which can made the precursor obviously well-distributed and influence the morphology of Cu(OH)2, consequently the kinetics of crystallization, which will further disturb the formation of impure phases.Secondly, the three-dimensionally layered silicate AMH-3 were obtained in the silica sol-Sr(OH)2-NaOH-H2O system with the absence of titanium, providing a simple and easy process for preparing AMH-3. Focused on the systems, the aggregative states of the silica sources is critical for the formation of AMH-3. An new phase Sr-1 was synthesized in the system, the results from XRD and TG analyses indicate that the sample has low thermal stability, and its framework structure is destroyed after calcined at 350℃Thirdly, using ethanol and acetone substitute the solvent of water partly, an new phase Sr-3 were gained from the organic solvent-water-silica sol systems successfully with the starting molar ratio of SiO2:0.35Na2O:0.16SrO:25.2H2O. The analyses indicate that in the TEOS-water system, TEOS can hydrolyze to SiO2 and C2H5OH, which can be consider as silica source and organic solvent respectively, thus the Sr-3 phase can obtained from the system. The results from XRD and TG analyses indicate that the samples have certain thermal stability, and its framework structure is still stable after calcined at 450℃.