The 24-membered ring - SYT type extra-large pore zeolite , denoted as DESO-SYSU-3, has been synthesized by employing N,N′-diethylsophoridine and trimethylsulfanium in a mixed-template system, where the N,N′-diethylsophoridine and trimethylsulfanium played different roles in the crystallization process . A single usage of N,N′-diethylsophoridine led to the formation of an unknown phase (donated as SYSU-5). These results reveal that the utilization of alkaloid-derived organic structure-directing agents (OSDAs) is an efficient synthetic strategy to produce specific extra-large pore zeolites and related structures. Compared to the prototype SYSU-3, the addition of TMSF into the system not only improved the silicon content in the framework of DESO-SYSU-3 but also facilitated the generation of carbon dots (CDs) confined in extra-large pore structure . The structure and the proposed formation mechanism of CDs were investigated based on HRTEM, XPS, FI-IR, UV–Vis, Raman and photoluminescence spectrum. The CDs@zeolite composite exhibited intriguing optical properties of both fluorescence and room temperature phosphorescence, respectively. This work extends extra-large pore zeolite as the matrix for the development of CDs@zeolite composites with tunable optical properties .
Azonia-spiro compounds have been reported as organic templates for synthesizing many extra-large pore high silica zeolites , often isomorphically substituted by germanium . However, these templates are usually obtained in the presence of sodium hydroxide, leading to persisting sodium ions in the final products. Sodium cations may compete with azonia-spiro organics as templates during zeolite synthesis. Therefore, effect of any residual sodium cations on the synthesis results needs to be investigated. This work documents the effect of sodium ions on zeolite formation using four structurally similar azonia-spiro compounds as templates. Different silicogermanate zeolites (UTL, an unknown zeolitic phase, etc.) were formed in the absence of sodium cations. Notably, the syntheses of silicogermanate UTL and siliceous MTW zeolites using azonia-spiro[4,6] and [6,6] are reported for the first time. Controlled amounts of sodium chloride were added to zeolite crystallization mixtures without residual sodium hydroxide. In the presence of 0.005–0.1 mol/L Na + , silicogermanate zeolites were the dominant phases. Further increasing the Na + concentration to 0.152 and 0.317 mol/L, formation of UTL and an unknown silicogermanate phase were inhibited in favor of a dense sodiumgermanate (Na 4 Ge 9 O 20 ). Moreover, sodium ions next to azonia-spiro organic templates also influence the morphologies of the MTW zeolites. The observed high sensitivity of zeolite formation in the presence of even traces of sodium therefore has impact on synthesis protocols of large pore silicogermanate zeolites. This work highlights how small, often overlooked, factors in inorganic material synthesis can drastically change the outcome.
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