The poor hydrothermal stability of germanosilicate zeolites greatly retards their industrial application. Herein, we present a direct synthesis of Ge-containing IWR zeolites with outstanding hydrothermal stability. A simple quaternary ammonium cation, diethyldimethylammonium, was used as the structure-directing agent for the first time. The structure and chemical composition of the framework was studied by performing Rietveld refinement of XRD data combined with electron microscopy, thermogravimetric and chemical analysis techniques. Al-free and Al-containing IWR zeolites were subjected to high-temperature vapor (973 K, 4 h), water-immersion (room temperature, 12 h) and treatment with 65% HNO solution (423 K, 24 h) to test their hydrothermal stability. Materials before and after hydrothermal treatments were characterized by complementary methods (XRD, FTIR, NMR and N sorption). The set of experimental data unambiguously proves the high stability of the zeolite framework.

Structure-directing agents (SDAs) play important roles in directing the formation of specific zeolite frameworks. Mechanisms and working hypothesis were proposed for understanding how SDAs work during the crystallization of zeolites. The lately reported cooperative structure-directing effect based on the investigation into the synthetic system containing both seed and organic species is one of them and is believed to be effective for synthesizing zeolites which are difficult to access or with novel structures. However, more examples are still needed to support the thesis. Herein, we report for the first time the syntheses of MTT -type zeolites with the simultaneous presences of octyltrimethylammonium chloride (OTMAC) and SFE zeolite seeds in the borosilicate system. SFE borosilicate zeolites serve as exotic seeds for the crystallization of MTT -type zeolites and together with OTMAC play cooperative structure-directing roles. Besides, Al,B- MTT and heteroatom (Zr, V, and Fe)-incorporated MTT -type zeolites were directly synthesized with the introduction of metal sources into the borosilicate system. Physicochemical properties of the obtained MTT zeolites were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, N 2 physisorption, NH 3 -TPD, 27 Al NMR, 13 C NMR, 11 B NMR, UV–visible spectroscopy, and UV Raman spectroscopy. The herein-reported phenomenon provides an example to better understand the mechanism of zeolite crystallization, and the synthesized zeolites may act as promising catalytic materials in several organic reactions.

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