摘要
Ni@Pd core-shell nanoparticles with a mean particle size of 8–9 nm were prepared by solvothermal reduction of bivalent nickel and palladium in oleylamine and trioctylphosphine.Subsequently,the first-ever deposition of Ni@Pd core-shell nanoparticles having different compositions on a metal-organic framework（MIL-101）was accomplished by wet impregnation in n-hexane.The Ni@Pd/MIL-101 materials were characterized by powder X-ray diffraction,Fourier transform infrared spectroscopy,transmission electron microscopy,and energy-dispersive X-ray spectroscopy and also investigated as catalysts for the hydrogenation of nitrobenzene under mild reaction conditions.At 30 °C and 0.1 MPa of H2 pressure,the Ni@Pd/MIL-101 gives a TOF as high as 375 h–1 for the hydrogenation of nitrobenzene and is applicable to a wide range of substituted nitroarenes.The exceptional performance of this catalyst is believed to result from the significant Ni-Pd interaction in the core-shell structure,together with promotion of the conversions of aromatics by uncoordinated Lewis acidic Cr sites on the MIL-101 support.
金属有机骨架(MOFs)材料是一种新型的沸石类多孔材料,是由金属离子和有机配体通过配位键键合而成的拓扑结构.相比其他多孔材料,MOFs拥有更高的比表面积、孔隙率以及结构可调控性.在催化方面,MOFs复合材料在多相催化领域已经引起了广泛的研究兴趣.贵金属纳米颗粒是一种在化学、化工、生物和医学等许多领域有着广泛应用的高性能材料.但是,催化反应往往都是发生在纳米颗粒的表面,而位于颗粒内部的金属没能得到利用;从原子经济性的角度来看,以廉价金属作核、贵金属作壳的双金属纳米粒子能有效解决这个问题,而且还能利用双金属之间的协调作用.目前文献中也己经报道了多种非贵金属和贵金属组成的核壳双金属纳米粒子,都展现出了比单纯贵金属更好的催化活性.芳香胺类化合物是一种在工业上非常重要的有机中间体,广泛应用于农药、药物、染料和色素等等.目前,商业化生产的芳香胺化合物都是通过计量的还原剂,如连二硫酸钠、硼氢化钠、水合肼和氨水中的铁、锡、锌等非催化还原相应的芳硝基化合物得到,这样往往会带来严重的环境污染问题.而通过多相催化加氢还原方法来制备芳香胺化合物,不仅能高效催化芳硝基化合物加氢,而且催化剂可以回收利用,大大降低反应对环境的污染.本文综合贵金属原子经济观点和芳硝基类化合物加氢反应催化剂设计,在油胺和三正辛基膦中通过热还原二价的镍和钯,制备出以Ni为核Pd为壳的双金属纳米粒子.通过透射电镜观察,镍钯核壳纳米粒子的粒径约为8-9 nm.选用具有高比表面积和高稳定性的金属有机骨架材料MIL-101作为载体,通过浸渍法首次将镍钯核壳纳米粒子负载在MIL-101上制备出不同Ni:Pd比的Ni@Pd/MIL-101复合材料.利用X射线粉末衍射(XRD)、N_2吸附-脱附、红外光谱、透射电子显微镜和X射线能谱对复�
基金
supported by the National Natural Science Foundation of China(21322606 and 21436005)
the Specialized Research Fund for the Doctoral Program of Higher Education(20120172110012)
the Fundamental Research Funds for the Central Universities
the Natural Science Foundation of Guangdong Province(S2011020002397 and 2013B090500027)~~
