MIL-53限域封装Ru纳米簇光催化固氮性能研究

Recently, photocatalytic nitrogen fixation technology has been widely concerned. The combination of MIL-53 and Ru nanocluster can effectively improve the performance of photocatalytic nitrogen fixation, while the particle size of Ru nanocluster and the interfacial property of Ru-MIL-53 are the critical factors. In order to achieve high efficient photocatalytic nitrogen fixation, this project is designed to encapsulate the Ru nanoclusters in the uniform pores of MIL-53 as N-N triple bond activation reaction center, the particle size of Ru nano-clusters can be regulated and their agglomeration can be avoided by the confinement effect of MIL-53, and the interfacial properties between Ru nano-cluster and MIL-53 are precisely controlled from the atomic scale. Based on modern spectral characterization and quantum chemical calculation, this project primary focuses on: 1) the regulation mechanism of the confinement effect of MIL-53 on the regulation mechanism of Ru nano-cluster size and nitrogen fixation performance; 2) the electron transfer pathway between MIL-53 and Ru nano-cluster; 3) the effect of the electronic density distribution of Ru-MOFs interfacial elements on nitrogen fixation; 4) the hydrogenation mechanism of N-N triple bond activation reduction. Finally, the intrinsic relationship between the Ru nanoparticles, the interfacial properties of MIL-53-Ru and the performance of nitrogen fixation will be obtained. The dependencies and change regulations between micro-molecular structure and macro-photocatalytic activity will be also understood. The new application of MOFs confinement encapsulation technology in the field of photocatalysis will be achieved. The obtained results will provide theoretical basis for the development of this novel efficient nitrogen fixation photocatalyst.

最近光催化固氮技术受到广泛关注。MIL-53与Ru纳米簇相结合能够有效提高光催化固氮性能，而Ru纳米簇的粒径及界面性质是关键因素。本项目拟在MIL-53规整孔道内限域封装Ru纳米簇充当氮氮三键活化反应中心，利用MIL-53的限域效应调控Ru纳米簇粒径并避免其发生团聚，从原子尺度上精确调控Ru纳米簇与MIL-53间的界面性质，实现高效光催化固氮之目的。结合现代表征与理论计算手段，重点研究：1）MIL-53限域效应对Ru纳米簇粒径的调控机制与固氮性能；2）MIL-53与Ru纳米簇间的电子传递途径；3）Ru-MIL-53界面元素电子密度分布对固氮的影响；4）氮氮三键活化加氢机制。最终得出Ru纳米簇粒径、Ru-MIL-53界面性质与固氮性能之间的内在联系，认识微观分子构效与宏观催化活性的依赖关系和变化规律，开辟MOFs材料限域封装技术在光催化领域的新应用，为新型高效固氮光催化剂的开发提供理论依据。

太阳能光催化固氮技术是实现温和条件合成氨的理想方法。然而，N≡N的高效光催化活化是亟待解决的难点性问题。基于此，本项目以在光催化剂表面构建高效活性中心点位（过渡金属、贵金属）为目标，构建金属-半导体复合光催化剂，依据所制复合催化剂的组成和金属与半导体间的微观空间架构，采用现代光谱表征、量化计算和性能测试相结合，重点研究了金属与半导体的相对含量、存在方式、空间架构、电子结构、分子特性、表面态、电子迁移特性，探讨了微观分子构效与宏观光催化活性的依赖关系和变化规律，研究表明：（1）MOFs中心金属的电子密度与光催化固氮活性具有直接关系，具有较高电子密度的中心金属有助于氮气分子活化；（2）在半导体中原位引入过渡金属Fe可实现对N2分子的活化；（3）调控贵金属与半导体之间的连接方式（空位填补与分子桥策略）能够有效提升氮气活化性能；（4）从传质角度出发开展了液固两相和气液固三相界面对难溶性N2光催化固定性能影响的研究；（5）金属-半导体复合光催化的构建能改变原半导体的带隙结构、电子分布状态、微观形貌、表面原子排布等进而促进其光催化性能的提高。该项工作为N≡N的高效光催化活化中心的构建提供了可靠的科学依据和理论基础，有望在催化剂制备及光催化氨合成领域得到应用。