甲苯选择性氧化高效光催化剂的可控制备及表/界面性质研究

The bottleneck in the photocatalytic conversion of toluene to benzaldehyde is the lack of catalysts of high efficiency. From a practical perspective, it is necessary to master the techniques for the adjustment of surface interfaces and to understand the mechanism of the photo-chemical reaction. Based on our previous works on visible-light-driven partial oxidation of toluene to benzaldehyde over bismuth-containing photocatalysts with high selectivity and efficiency, the following will be conducted in this project: (a) To prevent recombination of charge carriers through the use of co-catalysts, and to accelerate photochemical reaction by the creation of surface defects. (b) To obtain precise information on active sites and photocatalytic reaction mechanism using state-of-the-art in-situ techniques to study the adsorption and activation of toluene as well as desorption of benzaldehyde, and to track the reaction intermediate and the change of photocatalyst in the course of reaction. (c) To design new reactors suitable for solid-liquid-gas reaction and beneficial for the photocatalytic reaction based on mass-transfer and photo-reaction enhancement; this could be an important step toward large-scale production of benzaldehyde in photocatalytic process. It is envisioned that the outcome of the project is the establishment of environment-benign methods for the production of benzaldehyde, and the acquisition of important information for the design of high-efficiency photocatalysts for the capture of visible light for meaningful reactions.

开发高效光催化剂是实现甲苯选择性氧化制备苯甲醛所面临的最大瓶颈。获取可见光响应光催化材料的可控制备及表/界面处的微观光化学机制，是从机理层面上设计高性能光催化选择性氧化甲苯制备苯甲醛光催化剂的关键科学问题。本项目将基于前期研究工作的基础，以获得可见光下具有高活性和高选择性的铋系复合光催化剂为目标。拟通过铋自掺杂调控铋系化合物氧化能力，表面同时负载电子和空穴转移的助催化剂构建载流子转移通道，抑制载流子复合。表面氧缺陷位构筑提高表面光化学反应速率。借助先进原位表征技术跟踪反应过程催化剂表/界面反应物的活化历程和催化剂表/界面结构的变化情况以认识催化反应活性中心、揭示光化学反应机制。通过设计薄层平板式固定床光催化反应器促进固-液-气三相接触与传质，强化光催化反应过程。本项目的成功实施不仅有望为苯甲醛制备提供绿色清洁的生产工艺，同时为其他高效光催化材料的设计制备提供重要参考。

光催化甲苯选择性氧化制备苯甲醛具有反应条件温和、过程安全绿色等优点，本项目针对目前光催化剂存在活性和目标产物选择性难以兼得的不足，围绕光催化剂的可控制备与表/界面性质调控开展工作。基于三聚硫氰酸镉的可控分解，以三聚硫氰酸镉为原料，以超分子自组装法可控制备了一系列具有高比表面积、核壳结构、紧密异质结的CdS基光催化材料，其中CdS-CdIn2S4光催化剂催化甲苯转化率达到83%，苯甲醛选择性大于96%。通过水热、溶剂热等方法，成功制备超薄Bi2MoO6纳米片、将Bi2MoO6纳米颗粒负载于二维g-C3N4表面，实现Bi2MoO6高活性位点暴露，提高了可见光下甲苯选择性氧化制苯甲醛的性能。受B-位阳离子对钙钛矿光电性能影响的启发，使用Sb部分替代Bi制备了混合卤化物钙钛矿Cs3Bi2-xSbxBr9纳米片，揭示了在Cs3Bi2Br9中引入少量Sb不仅可以改善光吸收，而且能促进光生空穴的产生，光生空穴的表面局域能增强甲苯的吸附和C(sp3)-H键的解离。其中Cs3Bi1.8Sb0.2Br9纳米片甲苯的转化率达高到5830 mmol/g/h。以原位“刻蚀-再生长”法可控制备了三维有序大比表面积CdWO4/Bi2WO6、铁酸铋-MIL-53(Fe)，并将其分别应用于光催化有氧羟基化苯制苯酚，光催化苯甲醇选择性氧化制备苯甲醛等反应中，表现出好的光催化活性。创制了甲苯与卤苯光催化氧化偶联制备二苯甲酮光催化氧化胺化高选择性制备酰胺的绿色新工艺及高效催化剂。研制了以小分子咖啡酸为桥连剂，通过配位自组装法可控制备MOFs包覆BiVO4核壳结构催化材料的新方法，解决了传统方法包覆疏松不均匀的难题。