Controllable Construction Of Noble Metal/Metal Oxide Nanocatalyst Based-on Supramolecular Self-assembly

It is well known that noble metal nanoparticles(NPs)have excellent properties and extensive applications.However,the practical applications of ultra-small noble metal NPs suffer from poor stability and durability,thus requiring solid supports to prevent agglomeration,particle growth,and therefore a decrease in the total surface area.Compared to the naked ones,noble metal NPs supported on metal oxides with adjustable morphology and functionality not only exhibit excellent performance and stability,but also show the integration of functions.Therefore,it is important for scientific research and industrial development to study the controlled synthesis of noble metal/metal oxide nanocomposites.In spite of fast developments in research on the preparation and application of noble metal/metal oxide nanocomposites,there are still some significant challenges.First,although there are many reports on noble metal/metal oxide nanocomposites with special morphologies,the existing approaches are challenging in terms of the morphology control from 1D to 3D for a specific nanocomposite.Second,the effective control of the spatially uniform distribution of two kinds of the metal elements is difficult to realize.Third,high-yield preparation of selective growth of noble metal NPs on the high-surface-energy crystal facets of metal oxide is largely lacking with existing strategies.To solve the above problem,this paper presents a new method for the preparation of noble metal/metal oxide nanocomposites from dual metal coordination polymers as templates.The main work of this dissertation includes the following two aspects:First,we illustrate a facile route for the large-quantity fabrication of 1D Au/CaO nanocomposite catalysts by using bifunctional coordination polymers as precursors.Methacrylate anions(MAA-)with two distinct end groups are used as ligands in this study,and Ca(MAA)2/Au(Ⅲ)dual metal equipped coordination polymer are obtained through the self-assembly of MAA-with Ca2+,Au3+ ions under the desolvation effect.Furthermore,we gain insights into mechanism possibly responsible for the formation of coordination polymers with controlled morphologies.Then the Au/CaO nanoribbons are prepared through thermal decomposition of Ca(MAA)2/Au(Ⅲ)nanoribbons.Significantly,The as-synthesized 1D Au/CaO nanocatalysts showed high catalytic activity and stability in the transesterification reaction of soybean oil,which might be attributed to the small size and high distribution of CaO NPs as well as the special 1D structure with high surface areas.Moreover,the leaching and deactivation of the catalysts would be reduced owing to the presence of Au NPs on the surface of CaO nanoribbons.Second,in order to demonstrate the universality of the experimental method and the difference toward different metal ions,Zn(MAA)2/Pd(Ⅱ)nanocomposites with controllable morphology from 1D to 3D are prepared.Then the Pd/ZnO binary hollow superstructures are constructed through thermal decomposition of Zn(MAA)2/Pd(Ⅱ)precursors.Significantly,high-yield preparation of selective growth of Pd NPs on the ±(001)facets of ZnO matrix is achieved.Furthermore,the as-prepared Pd/ZnO composites exhibit excellent catalytic performance in the hydrogenation of p-nitrophenol to p-aminophenol with an excess amount of Na BH 4,which might be attributed to the small size and high distribution of the Pd NPs as well as the special hollow structures with high surface areas.Moreover,ZnO matrix with ±(001)bare facets have a synergistic catalytic effect with Pd NPs.And also the catalyst poisoning phenomenon would be inhibited owing to the presence of binary semiconductor-metal contacts.