Sn-containing Beta (Sn-Beta) zeolite is extensively applied in industrially-relevant reactions as a highly active and robust Lewis acid heterogeneous catalyst. Nonetheless, environmentally-unfriendly fluoride is generally required to the directly hydrothermal synthesis of Sn-Beta. In this work, an innovative strategy of interzeolite transformation with steam-assisted conversion is provided to directly synthesize Sn-Beta zeolite in the absence of fluoride. Silica source of FAU and steam-assisted conversion were two necessary factors for the successful synthesis of Sn-Beta zeolite. It was found that highly crystallized Sn-Beta zeolite with isolated framework Sn ions was hydrothermally synthesized via degradation of siliceous FAU zeolite and recrystallization of degraded silicate species. As far as we know, the crystal of Sn-Beta in this work was minimum in size among all present directly hydrothermal synthesized ones. More importantly, the Sn contents in Sn-Beta could achieved to 2.39 wt % (Si/Sn = 81), breaking through the Sn content restriction of conventional fluoride-mediated method. In addition, the hydrophobicity of this resultant Sn-Beta zeolite was slightly inferior to Sn-Beta-F obtained via traditional fluoride-assisted route. Whereas the smaller crystal size of this Sn-Beta gave rise to relatively good diffusion performance for organics, which made it reveal high activities in the Baeyer-Villiger oxidant of ketones in particular employing bulky tert-butyl hydroperoxide as the oxidant. The current strategy provides an alternative and environmentally-friendly method for the hydrothermal synthesis of Sn-Beta without the assistance of fluoride and alkali metal ions, which can guide further development in metallosilicates crystal engineering in terms of greenization.

含锡的Beta（Sn-Beta）沸石作为一种高活性和稳健的路易斯酸非均相催化剂，已广泛应用于与工业相关的反应中。但是，直接水热合成Sn-Beta通常需要对环境有害的氟化物。在这项工作中，提供了一种具有蒸汽辅助转化的沸石间转化的创新策略，可以在不存在氟化物的情况下直接合成Sn-Beta沸石。FAU的二氧化硅来源和蒸汽辅助转化是成功合成Sn-Beta沸石的两个必要因素。结果发现，通过硅质FAU沸石的降解和降解硅酸盐种类的重结晶，水热合成了具有分离的骨架锡离子的高度结晶的锡-β沸石。据我们所知，在所有现有的直接水热合成晶体中，这项工作中的Sn-β晶体尺寸最小。更重要的是，Sn-Beta中的Sn含量可以达到2.39 wt％（Si / Sn = 81），突破了常规氟化物介导方法对Sn含量的限制。另外，该所得的Sn-Beta沸石的疏水性略逊于通过传统的氟化物辅助途径获得的Sn-Beta-F。尽管这种Sn-Beta的晶体尺寸较小，但对有机物的扩散性能却相对较好，这使其在酮的Baeyer-Villiger氧化剂中表现出很高的活性，特别是在使用笨重的氧化剂时。突破了传统氟化物介导方法对锡含量的限制。另外，该所得的Sn-Beta沸石的疏水性略逊于通过传统的氟化物辅助途径获得的Sn-Beta-F。尽管这种Sn-Beta的晶体尺寸较小，但对有机物的扩散性能却相对较好，这使其在酮的Baeyer-Villiger氧化剂中表现出很高的活性，特别是在使用笨重的氧化剂时。突破了传统氟化物介导方法对锡含量的限制。另外，该所得的Sn-Beta沸石的疏水性略逊于通过传统的氟化物辅助途径获得的Sn-Beta-F。尽管这种Sn-Beta的晶体尺寸较小，但对有机物的扩散性能却相对较好，这使其在酮的Baeyer-Villiger氧化剂中表现出很高的活性，特别是在使用笨重的氧化剂时。叔丁基氢过氧化物为氧化剂。当前的策略提供了一种在不借助氟化物和碱金属离子的情况下水热合成Sn-β的环保方法，该方法可以指导金属硅酸盐晶体工程在绿色化方面的进一步发展。