Millimetre-scale HZSM-5 single crystals were successfully synthesized by a two-step hydrothermal method. In the first step, millimetre-sized silicalite-1 single crystals were prepared by hydrothermal synthesis using quartz tube as siliceous source. In the second step, framework Al atoms were inserted into the single crystals of silicalite-1 by another hydrothermal treatment involving NaAlO as aluminium source. Through the characterizations of power and single crystal X-ray diffraction, optical microscope, ICP, Al MAS NMR, Si MAS NMR, and -propylamine temperature-programmed decomposition (NPA-TPD), it was confirmed framework Al atoms with uniform spatial distribution can be inserted into giant single crystals of silicalite-1 with no obvious effects on the crystal structure, size and morphology. Such giant HZSM-5 single crystals are a promise candidate for the probe adsorption investigations, which can be applied in the measurement of framework Al spatial distribution. The strategy of insertion of aluminium or other heteroatoms of pure siliceous zeolite through secondary hydrothermal method provides a possible route to prepare giant single crystals that is difficult to synthesize directly.

中文翻译：

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二次水热处理合成毫米级HZSM-5单晶

采用两步水热法成功合成了毫米级HZSM-5单晶。第一步，以石英管为硅质源，通过水热合成法制备了毫米级的silicalite-1单晶。第二步，通过另一种涉及NaAlO作为铝源的水热处理，将骨架Al原子插入到silicalite-1的单晶中。通过功率和单晶X射线衍射、光学显微镜、ICP、Al MAS NMR、Si MAS NMR和丙胺程序升温分解(NPA-TPD)的表征，证实空间分布均匀的骨架Al原子可以插入巨大的silicalite-1单晶中，对晶体结构、尺寸和形貌没有明显影响。这种巨大的HZSM-5单晶是探针吸附研究的有希望的候选者，可应用于骨架Al空间分布的测量。通过二次水热法在纯硅质沸石中插入铝或其他杂原子的策略为制备难以直接合成的巨型单晶提供了可能的途径。