铂族金属纳米颗粒的形貌与其不对称催化氢化性能的构效关系研究

Study on the catalytic properties of platinum group metal nanoparticles with different morphologies and the structure-activity relationship between their morphologies and their catalytic performance for the asymmetric hydrogenation. Considering the difference of the enantioselectivity of the asymmetric hydrogenation of C=C and C=O, the cinchona alkaloid-modified platinum group metal nanoparticles with different morphologies will be used in the asymmetric catalytic hydrogenation of prochiral α,β-unsaturated acids and α-ketoesters. The interaction among platinum group metal nanoparticles with different morphologies, chiral modifier and substrate will be studied. The adsorption behaviors of solvent, chiral modifier, substrate on the surfaces of platinum group metal nanoparticles with different morphologies will be analysed. The adsorption modes and strength of the substrate molecules adsorbed to the surfaces of platinum group metal nanoparticles as well as desorption of the intermediate products and by-products will be also investigated. It will try to understand the interaction between substrate and chiral microenvironment or active sites, explain the effects of the morphologies, surface compositions and surface electronic structures of the metal nanoparticles on the catalytic activity and enantioselectivity of the asymmetric hydrogenation, probe the catalytic mechanism of the asymmetric hydrogenation on chiral modified platinum group metal nanoparticles with different morphologies, reveal the rules about the dependence of the catalytic properties of the asymmetric hydrogenation upon the morphologies of the platinum group metal nanoparticles. This research will provide a new approach to develop heterogeneous asymmetric hydrogenation system with high performance.

研究不同形貌铂族金属纳米簇的不对称催化氢化性能，考察铂族金属纳米颗粒的形貌与其不对称催化氢化性能间的构效关系。结合不同铂族金属对C=C和C=O双键不对称氢化选择性的差异，利用金鸡纳碱修饰的不同形貌金属Pd、Pt纳米颗粒催化前手性α,β-不饱和酸和α-酮酸酯的不对称氢化反应，研究不同形貌铂族金属纳米颗粒与手性修饰剂及反应底物的相互作用，分析溶剂、修饰剂及反应底物在不同形貌铂族金属纳米颗粒表面的吸附行为，考察在一定形貌铂族金属纳米颗粒表面上反应底物的吸附模式、吸附强度、中间产物的脱附、副产物的脱附，理解手性微环境及活性位点与反应底物间的关系，阐明铂族金属纳米颗粒的形貌、表面组成和表面电子结构对不对称氢化反应的催化活性及对映选择性的影响，探讨不同形貌铂族金属催化不对称氢化反应的作用机理，揭示铂族金属纳米颗粒形貌与其不对称催化氢化性能间相关性的规律，为建立新型、高效的多相不对称催化体系提供新途径。

金属纳米颗粒的形貌调控是研究其催化性能形貌相关性的基础，其性质与颗粒大小、形貌、组成及表面结构密切相关。特定形貌的铂族金属纳米颗粒在电催化氧化、氧还原及其它化学反应中均表现出较高的催化活性和良好的选择性，且具有明显的形貌相关性。迄今为止，虽然铂族金属纳米颗粒的形貌控制合成已经取得较大进展，但是具有特定形貌的铂族金属及其合金纳米晶的快速合成仍是该领域的巨大挑战。为此，本项目主要开展铂族金属及其合金纳米颗粒的形貌控制合成、表征及其催化性能研究，合成得到一系列特定形貌的铂族金属及其合金纳米晶，并对其催化性能进行了初步探索。采用微波法，成功制备了八角形铂纳米晶、Pd-Pt合金超立方体纳米晶、截角三八面体及八面体Pt-Au合金纳米晶、凹八面体Pt-Cu合金纳米晶、Pd-Rh空心立方体合金纳米晶、Pt-Rh凹立方体合金纳米晶等，与商业铂黑或Pd黑相比，这些合金纳米晶对甲醇或甲酸的电催化氧化活性显著增强。采用油浴法合成了多级四足形Pd纳米晶、多级树枝状Pd纳米晶、多级凹面四足形Pd纳米晶、圆形Pd纳米片自组装体以及Pd-Au合金二十面体纳米晶等，与商业Pd黑相比，所得到的不同形貌Pd纳米晶及其合金纳米晶对甲醇或甲酸的电催化氧化活性均显著增强。这些具有一定形貌的铂族金属及其合金纳米晶的成功合成为进一步考察其催化性能的构效关系奠定了基础。