科研之友
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摘要
Selective hydrogenation of quinoline toward 1,2,3,4-tetrahydroquinoline shows great application potential in the production of medicine, pesticides and fine chemicals. However, the hydrogenation of quinoline is usually carried out under harsh reaction conditions such as high temperature and high pressure, and thus, it is a great challenge to achieve selective hydrogenation of quinoline under mild conditions. In this work, we construct platinum nanoparticles (Pt NPs) sandwiched in an inner core and an outer shell composed of a metal-organic framework synthesized by zirconium chloride and 2,2'-bipyridine-5,5'-dicarboxylic acid (known as UiO-67N). Different sandwich structures with shell thickness of 11, 28 and 42 nm are precisely prepared. The obtained catalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), inductively coupled plasma emission spectrometer (ICP-OES), Fourier transform infrared spectroscopy (FTIR) and nitrogen adsorption and desorption. Impressively, the selective hydrogenation of quinoline over Pt NPs is significantly enhanced by using UiO-67N as support in respect with UiO-67. Moreover, UiO-67N@Pt@UiO-67N exhibits the selective hydrogenation of quinoline with high conversion rate (>99%) and high selectivity of 1,2,3,4-tetrahydroisoquinoline (>99%) at room temperature. The shell thickness has significant influence on the catalytic activity of Pt NPs, and with increasing the shell thickness from 11 to 42 nm, the conversion rate decreases from 99% to 53.5% under the identical conditions, while the selectivity of 1,2,3,4-tetrahydroisoquinoline is well kept. When other derivatives of quinoline are used as substrates, the excellent activity and selectivity are also achieved over sandwich catalysts. Besides, the UiO-67N@Pt@UiO-67N catalyst could be used at least 5 times without obvious deactivation, but the significant deactivation happens over supported UiO-67N@Pt catalyst. XPS and FTIR measurements show that the excellent catalytic performance mainly originates from the electron transfer between UiO-67N and Pt NPs, and the strong interfacial interaction between UiO-67N and quinoline.
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