The titanium species and structure-performance relationship in boron-free Ti-MWW zeolite have been thoroughly studied by 244 nm excited UV resonance Raman spectroscopy for the first time. It was surprisingly found out that acid treatment not only removed a part of the dominant non-framework TiO_m (m = 5, 6) species but also made most of them transformed into TiO₄ species, which has never been reported before. Interestingly, acid treatment of as-synthesized and directly calcined Ti-MWW resulted in the formation of active framework TiO₄ species and inactive TiO₄ species in amorphous SiO₂ matrix, respectively. Only the samples obtained from acid treatment of as-synthesized Ti-MWW and subsequent calcination showed catalytic activity in 1-hexene epoxidation. Importantly, despite higher Si/Ti ratio, framework Ti(OSi)₄ species-dominant Ti-MWW showed better catalytic performance than the relatively hydrophilic framework Ti(OSi)₃OH species-dominant one. These understandings would be beneficial for further study of Ti-MWW and development of highly efficient titanosilicate zeolites.

首次通过244 nm激发紫外共振拉曼光谱研究了无硼Ti-MWW沸石中的钛种类和结构-性能关系。令人惊讶地发现，酸处理不仅去除了一部分占主导地位的非骨架TiO _m（m = 5、6）物种，而且使它们中的大多数转变为TiO ₄物种，这是从未有过的报道。有趣的是，对合成后直接煅烧的Ti-MWW进行酸处理会导致在无定形SiO _2中形成活性骨架TiO ₄物种和惰性TiO ₄物种。矩阵。仅从酸处理的合成Ti-MWW和随后的煅烧中获得的样品在1-己烯环氧化中显示催化活性。重要的是，尽管较高的Si / Ti比，但骨架Ti（OSi）₄占优势的Ti-MWW比相对亲水的骨架Ti（OSi）₃ OH占优势的催化剂表现出更好的催化性能。这些认识将有助于进一步研究Ti-MWW和开发高效钛硅酸盐沸石。