Department of Chemical Engineering, University of Massachusetts Amherst, 686 N Pleasant St, Amherst, MA, 01003, USA.
Department of Polymer Science & Engineering, University of Massachusetts Amherst, 120 Governor's Dr, Amherst, MA, 01003, USA.
Angew Chem Int Ed Engl. 2018 Mar 26;57(14):3607-3611. doi: 10.1002/anie.201712684. Epub 2018 Feb 21.
Siliceous zeolites are ideally suited for emerging applications in gas separations, sensors, and the next generation of low-k dielectric materials, but the use of fluoride in the synthesis significantly hinders their commercialization. Herein, we show that the dry gel conversion (DGC) technique can overcome this problem. Fluoride-free synthesis of two siliceous zeolites-AMH-4 (CHA-type) and AMH-5 (STT-type), has been achieved for the first time using the method. Siliceous *BEA-, MFI-, and *MRE-type zeolites have also been synthesized to obtain insights into the crystallization process. Charge-balancing interactions between the inorganic cation, organic structure-directing agent (OSDA), and Si-O defects are found to be an essential aspect. We quantify this factor in terms of the "OSDA charge/silica ratio" of the as-made zeolites and demonstrate that the DGC technique is broadly applicable and opens up new avenues for fluoride-free siliceous zeolite synthesis.
硅沸石非常适合新兴的气体分离、传感器和下一代低 k 介电材料的应用，但氟化物在合成中的使用严重阻碍了它们的商业化。在此，我们表明干凝胶转化（DGC）技术可以克服这个问题。首次使用该方法实现了无氟合成两种硅沸石-AMH-4（CHA 型）和 AMH-5（STT 型）。还合成了硅 *BEA-、MFI-和 *MRE-型沸石，以深入了解结晶过程。发现无机阳离子、有机结构导向剂（OSDA）和 Si-O 缺陷之间的电荷平衡相互作用是一个重要方面。我们用所制沸石的“OSDA 电荷/二氧化硅比”来定量这个因素，并证明 DGC 技术具有广泛的适用性，并为无氟硅沸石合成开辟了新途径。
