CuCl与SiO_2-TiO_2载体相互作用的密度泛函理论研究

以SiO2簇模型为基体,通过Ti原子取代建立Ti中心原子上连接0个或1个OH基团的典型SiO2-TiO2复合氧化物模型来模拟处于体相中和表面上的四配位Ti(IV)中心.采用广义梯度近似的密度泛函理论(DFT-GGA)研究了CuCl与SiO2-TiO2载体的相互作用.计算结果表明,在SiO2基体中嵌入Ti(IV)离子可以大大加强CuCl与氧化物载体之间的相互作用,使CuCl/SiO2-TiO2催化剂的结构更稳定.分子前线轨道表明Cu(I)作为催化剂的活性中心贡献了HOMO轨道,容易失去电子;Ti(IV)中心原子贡献LUMO轨道,容易得到电子,计算结果与实验事实相一致.

A Density Functional Theory Study of Interaction of CuCl with Silica-titania Supports

The clusters contain 0 and 1 hydroxyl groups at the titanium center, noted as Ti_bulkSi₄Si₆ and Ti_suf(OH)Si₃Si₆, respectively, were used to simulate the Ti(IV) center in the silica matrix. The interactions of CuCl with SiO₂-TiO₂ mixed oxide were systematically studied by the first-principle DFT-GGA calculations. The calculation results show that incorporation of Ti atoms into silica can enhance the interaction of CuCl with the oxide support, leading to more stable CuCl/SiO₂-TiO₂ catalysts. In addition, the frontier molecular orbital shows that the HOMO orbits of the CuCl/Ti_bulkSi₄Si₆and CuCl/Ti_suf(OH)Si₃Si₆ adsorbed clusters were mainly contributed by Cu atoms, while the LUMO orbits were contributed by Ti atoms. The calculation results were in accordance with the experimental facts.