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

本研究中，我们提出了一种利用金属络合物吸附和分子印迹技术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。以金属配合物的配体为模板分子，在活性金属中心上形成与模板配体形状相似的空穴，作为表面的择形反应空间。我们制备了在二氧化硅、氧化铝和二氧化钛表面上的钯单体催化剂用于烯烃氢胺化反应，一系列负载在二氧化硅表面上的含金属离子液体，分子印迹的二氧化硅上的铑络合物催化剂，以及位于H-ZSM-5中的N-间隙Re簇。采用FT-IR、NMR、UV/维斯、ESR、XRD、XRF、BET、ICP、拉曼、XPS、XAFS和DFT等方法对催化剂的结构进行了表征。采用时间分辨能量色散X射线荧光光谱（DXAFS）研究了活性金属催化剂的结构动力学，揭示了催化剂的表面催化反应机理以及活性金属中心的结构与催化性能的关系。我们发现了钒席夫碱单体在二氧化硅表面上的新型手性自二聚反应，以及用非手性硅烷偶联剂进行表面官能化，从而促进了负载的Cu-氧化硅表面上的BOX催化剂。所得手性V二聚体非均相催化剂对2-萘酚的不对称氧化偶联反应具有较高的催化活性、100%的选择性和对映选择性。表面功能化的Cu-BOX催化剂显著提高了不对称Diels-Alder反应的对映选择性。这些技术是有前途的方法来开发氧化物表面上的不对称多相催化剂。

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.