The spectroscopic features of the Ti-hydroperoxo intermediates in TS-1, Ti-BEA, and Ti-YNU-1 zeolites were studied by using theoretical calculations. The Ti-hydroperoxo intermediates, Ti-η¹(OOH), Ti-η¹(OOH)-H₂O, Ti-η²(OOH), and Ti-η²(OOH)-H₂O species, as well as Ti-η¹(OOH)-CH₃OH, Ti-η¹(OOH)-CH₃CN, Ti-η²(OOH)-CH₃OH, and Ti-η²(OOH)-CH₃CN species were constructed and their IR, Raman, and UV-vis spectra were calculated. The geometry optimization and vibrational frequency calculations were carried out with DFT method at the theoretical level of B3LYP/6-31G(d, p), and the UV-vis spectra were obtained with TD-DFT method at the theoretical level of PBEPBE/6-311++G(d, p). The calculated structures show the average Ti–O bond distances of 2.01±0.02 Å, consistent well with the experimental EXAFS data reported in the literatures. The calculated IR and Raman spectra of Ti-hydroperoxo intermediates show that the O_α–O_β stretching vibrations are in the range of 870-910 cm^-1 for Ti-η¹(OOH) and Ti-η¹(OOH)-R (R = H₂O, CH₃OH, CH₃CN) species, and 834-855 cm^-1 for Ti-η²(OOH) and Ti-η²(OOH)-R species. TD-DFT calculations indicate that for Ti-η¹(OOH) and Ti-η¹(OOH)-R species, the transition wavelengths are in the range of 350-365 nm and 370-400 nm, respectively, which are ascribed to the electron transition from the p orbital of the active oxygen O_α and O_β to the unoccupied d* orbital of framework Ti atom, being responsible for the 385 nm band observed in the experimental UV-vis spectrum of TS-1 zeolite as contacting with H₂O₂ aqueous solution. Whereas, for the Ti-η²(OOH) and Ti-η²(OOH)-R species, all the corresponding transitions are below 350 nm. The catalytic performances of the Ti-hydroperoxo intermediates for olefin epoxidation were also evaluated. In combination of the calculated geometric parameters, the stabilities, the spectroscopic properties, and the catalytic performances, it is demonstrated that the initially formed Ti-hydroperoxo intermediates in titanosilicate/H₂O₂/H₂O system should be Ti-η¹(OOH)-H₂O or Ti-η¹(OOH) species, which then converts into the more stable Ti-η²(OOH)-H₂O species that works as the actual catalytic active center for epoxidation reactions. If the solvent is methanol or acetonitrile, Ti-η²(OOH)-CH₃OH or Ti-η²(OOH)-CH₃CN species should be the predominant active center.

通过理论计算，研究了TS-1，Ti-BEA和Ti-YNU-1沸石中Ti-氢过氧中间体的光谱特征。在Ti-氢过中间体，的Ti-η ¹（OOH），的Ti-η ¹（OOH）-H ₂ O，的Ti-η ²（OOH）和Ti-η ²（OOH）-H ₂ O类物质，以及以Ti-η ¹（OOH）-CH ₃ OH，的Ti-η ¹（OOH）-CH ₃ CN，的Ti-η ²（OOH）-CH ₃ OH，和Ti-η ²（OOH）-CH ₃构建了CN物种，并计算了它们的IR，拉曼光谱和UV-可见光谱。在理论水平B3LYP / 6-31G（d，p）上用DFT方法进行了几何优化和振动频率计算，在理论水平PBPBBE / 6上用TD-DFT方法获得了紫外可见光谱-311 ++ G（d，p）。计算得出的结构显示平均Ti–O键距为2.01±0.02Å，与文献中报道的EXAFS实验数据吻合良好。的Ti-氢过中间体的计算IR和拉曼光谱表明，将O _α -O _β伸缩振动是在870-910厘米的范围^-1为TI-η ¹（OOH）和Ti-η ¹（OOH）-R （R = H ₂ O，CH₃ OH，CH ₃ CN）物种，和834-855厘米^-1为TI-η ²（OOH）和Ti-η ²（OOH）-R物种。TD-DFT计算表明，对于Ti系η ¹（OOH）和Ti-η ¹（OOH）-R物种，过渡波长分别是在350-365纳米和370-400纳米的范围内，这是归因于从电子跃迁p轨道的活性氧的O- _α和O _β到未被占用的d轨道框架Ti原子，负责在TS-1沸石的实验的UV-vis光谱中观察到与接触385纳米带* H ₂ O ₂水溶液。而对于在Ti-η ²（OOH）和Ti-η ²（OOH）-R物种，所有相应的转换是350nm以下。还评估了Ti-氢过氧中间体对烯烃环氧化的催化性能。在所计算的几何参数，在稳定性，光谱性质，和催化性能的组合，可以证明，在钛硅酸盐/ H最初形成的Ti-氢过中间体₂ ö ₂ / H ₂ O系统应该是Ti-η ¹（ OOH）-H ₂ O或Ti系η ¹（OOH）物种，然后转换成更稳定的Ti-η ²（OOH）-H ₂用作环氧化反应的实际催化活性中心的O类。如果溶剂是甲醇或乙腈，的Ti-η ²（OOH）-CH ₃ OH或Ti-η ²（OOH）-CH ₃ CN物种应该是主要的活性中心。