Concave Silica Nanosphere with a Functionalized Open-Mouthed Cavity as Highly Active and Durable Catalytic Nanoreactor
作者:Jin Goo Kim、Amit Kumar、Seung Jin Lee、Junghoon Kim、Dong-Gyu Lee、Taewan Kwon、Seung Hwan Cho、In Su Lee
DOI:10.1021/acs.chemmater.7b02235
日期:2017.9.26
Despite increasingly intensive research into catalytic hollow nanoreactors, most of the work has focused on the enclosed cavity structure, and attempts to use the open-mouthed cavity have not been made so far, most likely due to the lack of methodologies for producing and functionalizing such a structure. This paper reports a synthetic strategy toward open-mouthed cavity-based nanoreactors, which renders the SiO2 nanosphere with a concave surface and also immobilizes catalytic nanocrystals (NCs) specifically inside the concave region. By putting the Janus silica-encapsulated manganese oxide (MnO) nanoparticle, with its highly off-centered core@shell structure, through the thermal hollow-conversion process, the edge-touching MnO nanoparticle was transformed into a hollow hemispherical manganese silicate layer with an opening to the outside, thus producing the bitten apple-like structure, conc-(Ni/HMS)@SiO2, with an open-mouthed cavity on the SiO2 nanosphere. The galvanic replacement reaction occurring on the manganese-silicate layer of the conc-(Ni/HMS)@SiO2 afforded the site-specific immobilization of catalytic Pt NCs on the preformed concave interior surface, signifying the possible postsynthetic functionalization of an open-mouthed cavity which could be adapted for the development of a nanoreactor system. The newly developed nanoreactor, Pt@conc-SiO2, carrying tiny catalytic Pt NCs inside the semiexposed and also semiprotected pocket-like space, exhibited an increased reaction rate and a more extended range of applicable substrates in catalyzing the reduction of nitroarene compounds, compared with the enclosed cavity-based analogue, while preserving the high immobilization stability of Pt nanocatalysts during the recycling process.
尽管对催化空心纳米反应器的研究越来越深入,但大部分工作都集中在封闭空腔结构上,迄今为止还没有尝试使用开口空腔,这很可能是由于缺乏生产和功能化这种结构的方法。本文报告了一种基于开口空腔的纳米反应器的合成策略,它使二氧化硅纳米球具有凹面,并将催化纳米晶体(NC)专门固定在凹面区域内。通过将具有高度偏心核@壳结构的 Janus 硅胶封装氧化锰(MnO)纳米粒子置于热空心转换过程中,接触边缘的 MnO 纳米粒子转变为向外开口的中空半球形硅酸锰层,从而在二氧化硅纳米球上产生了具有开口空腔的咬苹果状结构 conc-(Ni/HMS)@SiO2 。在 conc-(Ni/HMS)@SiO2 的硅酸锰层上发生的电化学置换反应使催化铂数控元素被固定在预形成的凹形内表面上,这意味着可以对开口空腔进行合成后功能化,从而用于开发纳米反应器系统。与封闭式空腔类似物相比,新开发的 Pt@conc-SiO2 纳米反应器在半暴露和半保护的口袋状空间内携带了微小的催化铂数控元素,在催化硝基烯烃化合物还原过程中显示出更高的反应速率和更大的适用底物范围,同时在回收过程中保持了铂纳米催化剂的高固定稳定性。