Design of Molecular-Imprinted Metal-Complex Catalysts at Surfaces for Shape-Selective and Asymmetric Catalysis

在本研究中，我们提出了一种通过金属络合物吸附和分子印迹来设计催化活性表面的方法，并成功地在氧化物表面制备了新型负载型金属络合物催化剂。以附着的金属络合物的配体作为模板分子，在活性金属中心形成与模板配体形状相似的空腔，作为表面择形反应空间。我们在二氧化硅、氧化铝和二氧化钛表面制备了用于烯烃氢胺化反应的Pd单体催化剂，在二氧化硅表面负载了一系列含金属离子液体，在二氧化硅表面制备了分子印迹Rh络合物催化剂，并在H-ZSM-5分子筛上制备了N-间隙Re簇合物。考察了负载型金属络合物催化剂的催化性能，用FT-IR、核磁共振、UV/Vis、ESR、X-射线荧光光谱、比表面积、电感耦合等离子体、拉曼光谱、X-射线光电子能谱、X-射线光电子能谱和密度泛函理论等手段对催化剂的结构进行了表征。用时间分辨能量色散X射线光电子能谱(DXAFS)研究了活性金属催化剂的结构动力学，揭示了它们在表面上的催化反应机理以及活性金属中心结构与其催化性能的关系。对于多相表面上的不对称催化，我们发现了二氧化硅表面上新型的钒席夫碱单体的手性自二聚反应和硅烷偶联剂对二氧化硅表面负载型铜盒催化剂上促进对映选择性的表面官能化。得到的手性V二聚体多相催化剂对2-萘酚的不对称氧化偶联反应具有催化活性、100%的选择性和较高的对映选择性。表面功能化的铜盒催化剂显著提高了不对称Diels-Alder反应的对映选择性。这些技术是在氧化物表面开发不对称多相催化剂的很有前途的方法。

In this study, we proposed a designs of catalytically active surfaces by metal-complex attaching and molecular imprinting and succeeded in the preparation of novel supported metal-complex catalysts on oxide surfaces. A ligand of an attached metal complex is used as a template molecule and a cavity with similar shape to the template ligand is created on the active metal center, which acts as shape-selective reaction space on the surface. We prepared Pd-monomer catalysts on silica, alumina, and titania surfaces for alkene hydroamination, a series of metal-containing ionic liquid supported on silica surfaces, molecular-imprinted Rh-complex catalysts on silica, and N-interstitial Re clusters located in H-ZSM-5. The catalytic performances of these supported metal-complex catalysts were investigated.The structures of the prepared metal-complex catalysts were characterized by means of FT-IR, NMR, UV/VIS, ESR XRD, XRF, BET, ICP, Raman, XPS, XAFS and DFT calculations. The structural kinetics of the active metal catalysts were investigated by time-resolved energy-dispersive XAFS(DXAFS) with ms time resolution, and their catalytic reaction mechanism on surfaces and the relationship between the structures of active metal centers and their catalysis were demonstrated.For asymmetric catalysis on heterogeneous surfaces, we found the novel chiral self-dimerization of vanadium Schiff-base monomers on a silica surface and surface functionalizaiton with achial silane-coupling reagents promoting enantioselectivity on supported Cu-BOX catalysts on a silica surface. The obtained heterogeneous catalysts of chiral V dimers exhibited catalytic activity, 100% selectivity and high enantioselectivity for the asymmetric oxidative coupling of 2-naphthol. The surface-functionalized Cu-BOX catalyst dramatically increased enantioselectivity for asymmetric Diels-Alder reaction. These techniques are promising ways to develop asymmetric heterogeneous catalysts on oxide surfaces.