The design of highly enantioselective heterogeneous catalysts offers an efficient route for the production of enantiopure chiral molecules, which are crucial intermediates in the pharmaceutical, agrochemical, and fine chemical industries. In this study, we present a strategy to enhance the enantioselectivity of supported Pt catalysts for the hydrogenation of α-keto esters by modifying SiO2 supports with poly(ethyleneimine) (PEI), a nitrogen-rich polymer. By adjusting the heat-treatment time, the quantity of PEI-derived residues on the support was successfully controlled, thereby fine-tuning the electronic state of Pt through electron-transfer interactions, and resulting in the generation of positively charged Pt species. Catalytic evaluations showed that the Pt/PEI-SiO2 catalysts exhibited superior enantioselectivities compared to the unmodified Pt/SiO2, with an optimal performance of 96.1% enantiomeric excess (ee). In addition, the Pt/PEI-SiO2 catalysts exhibited high enantioselectivities using various α-keto esters, chiral modifiers, and H2 pressures, as well as an excellent reusability over ten consecutive cycles. The observed correlation between the higher proportion of positively charged Pt species and the increased ee suggests that the improved enantioselectivity of the Pt/PEI-SiO2 catalyst system is driven by the enhanced adsorption of chiral modifiers, which is facilitated by interactions between the anchoring moiety and the electron-deficient Pt surface. These findings highlight the essential role of interactions between the active metals and the modifying organic species bound to support materials in enhancing the enantioselectivity. Moreover, they provide valuable insights for catalyst design through electronic tuning of the active metal surface with organic-modified supports.

中文翻译：

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含 N 聚合物对 SiO2 载体进行表面改性，在 Pt 催化剂上进行对映选择性加氢

高对映选择性多相催化剂的设计为对映手性分子的生产提供了一条有效的途径，对映手分子是制药、农化和精细化工行业的关键中间体。在这项研究中，我们提出了一种策略，通过用富氮聚合物聚乙烯亚胺（PEI）改性 SiO2 载体来增强负载 Pt 催化剂的对映选择性，用于α酮酯的氢化。通过调节热处理时间，成功控制了载体上 PEI 衍生的残基数量，从而通过电子转移相互作用微调 Pt 的电子态，从而产生带正电的 Pt 物质。催化评价表明，与未改性的 Pt/SiO2 相比，Pt/PEI-SiO2 催化剂表现出优异的对映选择性，其最佳性能为 96.1%对映体过量（ee）。此外，Pt/PEI-SiO2 催化剂在使用各种α酮酯、手性改性剂和 H2 压力时表现出高对映选择性，并在连续十个循环中表现出出色的可重复使用性。观察到的带正电的 Pt 物质比例较高与 ee 增加之间的相关性表明，Pt/PEI-SiO2 催化剂体系的对映选择性的提高是由手性改性剂的增强吸附驱动的，而锚定部分和缺电子 Pt 表面之间的相互作用促进了这种吸附。这些发现强调了活性金属与与支撑材料结合的修饰有机物质之间的相互作用在增强对映选择性方面的重要作用。 此外，它们通过使用有机改性载体对活性金属表面进行电子调谐，为催化剂设计提供了宝贵的见解。