含硫树状多配体调制催化贵金属纳米束及其补丁约束效应

金属催化剂的活性、耐用性和泄漏性取决于其配体/载体的电子结构与物理形态。本项目致力于以结构化载体负载补丁约束的贵金属纳米束(NC)以获取绿色耐用催化材料。在超支化聚乙撑亚胺（PEI）上引入微量强配体硫醇/硫醚，能和氨基弱配体协同作用获得尺寸小、活性高且性能稳定的复合纳米束(NC-PEI)。对NC-PEI进行弱亲油化获得水溶性树状复合两亲体，后者在小分子表面活性剂辅助下共同稳定乳液。待乳液粒固化后除去辅助剂，表面将仅留下由分立树状体补丁约束的NC。反之，对NC-PEI进行充分亲油化，则可通过油包水型浓乳液调制三维通孔骨架，骨架的孔表面类似地仅由分立补丁约束的NC表达。分立补丁能抑制NC的老化和原子态流失。总之，含硫树状配体能调制高质量NC的合成，引导NC在结构化载体表面表达，并作为补丁约束NC。这类易回收NC催化效率高、同时可显著降低产品和介质中的贵金属残留。

The activity, durability and recyclability of metallic catalyst lie on the morphological and chemical environment of the metal ligands/supports. This project dedicates to structured ligands to mediate and support green metal nanocluster (NC) catalysts. Introduction of a few thiol/thioether groups to branched polyethylenimine (PEI) so that the thio- and amino groups cooperatively mediate synthesis of quality, active and stable NC nanocoomposite (termed NC-PEI). Slight alkylation of NC-PEI leads to a water-soluble amphiphilic NC composite. The NC-composite can costabilize an oil-in-water emulsion with small surfactants and, after solidification and full washing, NC-composite dictates the surface of the resulting emulsion-based particle as discrete patches. Similarly, for sufficiently alkylated NC-PEI composite, it can lead to an open-cellular monolith via a water-in-oil concentric emulsion, with the monolith’s pore surface dictated by discrete NC-impregnated patches. The discrete patches suppress NC from erosion and ripening. In a word, the dendritic amphiphile can mediate synthesis of quality NC, direct its dictation exclusively on support surface, and confine NC by patch. Such NC is catalytically efficient and well recyclable, and can significantly decrease metal content in either product or medium.