Rhodium nanoparticle encapsulated in a porous carbon shell as an active heterogeneous catalyst for aromatic hydrogenation
Rhodium nanoparticle encapsulated in a porous carbon shell as an active heterogeneous catalyst for aromatic hydrogenation
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DOI：
10.1002/adfm.200701442
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发表时间：
2008-08-11
影响因子：
19
通讯作者：
Matsumura, Michio
中科院分区：
文献类型：
--
作者：
Harada, Takashi;Ikeda, Shigeru;Matsumura, Michio
通过在铑纳米颗粒上双层包覆二氧化硅层和介孔二氧化硅/碳层，然后用氢氟酸水溶液化学蚀刻除去硅质组分，制备了铑（Rh）纳米颗粒（核）-碳（壳）粉末。使用各种技术表征的结构表明，由此获得的粉末具有摇铃状结构：Rh纳米粒子被封装在具有发达的孔隙率的中空碳壳中。侧碳壳的多孔壁结构提供通道和疏水空隙空间，其允许存在于水性介质中的有机物质的有效渗透和吸收。这提供了壳内具有高浓度有机底物的微环境。此外，中间Rh纳米颗粒的表面不含任何配体，即，暴露活性表面位点以诱导有机转化。这些独特的性质，这是不能实现的常规Rh纳米粒子稳定的有机试剂，导致了优异的催化活性，氢化各种芳环和杂环在水中。
Rhodium (Rh) nanoparticle (core)-carbon (shell) powder was prepared by double-layer coating of a silica layer and a mesoporous silica/carbon layer on an Rh nanoparticle followed by chemical etching with aqueous hydrofluoric acid to remove siliceous components. The use of various techniques for characterization of the structure showed that the powder thus-obtained had a rattle-like structure: Rh nanoparticles were encapsulated in the hollow carbon-shell having well-developed porosity. The porous wall structure of the lateral carbon shell provides channels and hydrophobic void spaces that allow efficient penetration and absorption of organic species present in aqueous media. This offers a microenvironment with a high concentration of organic substrates inside the shell. Moreover, the surfaces of medial Rh nanoparticles were free from any ligands, i.e., the active surface site(s) was exposed to induce organic transformations. These unique properties, which cannot be achieved by conventional Rh nanoparticles stabilized with organic agents, led to excellent catalytic activity for hydrogenation of various aromatic and heterocyclic rings in water.