Platinum Nanoparticles Supported on Nitrogen‐doped Carbon Nanofibers as Efficient Poisoning Catalysts for the Hydrogenation of Nitroarenes
Platinum Nanoparticles Supported on Nitrogen‐doped Carbon Nanofibers as Efficient Poisoning Catalysts for the Hydrogenation of Nitroarenes
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DOI：
10.1002/cctc.201100135
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发表时间：
2011-10
期刊：
影响因子：
4.5
通讯作者：
Yukihiro Motoyama;Youngjin Lee;K. Tsuji;Seong-Ho Yoon;I. Mochida;H. Nagashima
中科院分区：
文献类型：
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作者：
Yukihiro Motoyama;Youngjin Lee;K. Tsuji;Seong-Ho Yoon;I. Mochida;H. Nagashima
碳载金属纳米粒子广泛用作传感器、燃料电池和锂离子电池的电催化剂或各种有机转化的多相催化剂。由于这些材料的催化性能高度依赖于载体，因此已经进行了大量研究来改性碳载体以提高其催化剂性能。 2] 调整化学和/或物理特性并稳定金属纳米颗粒-载体相互作用的一种方法涉及通过引入官能团或掺杂杂原子对碳表面进行化学改性。例如，在原始催化剂中添加硫、氮、磷或卤素化合物作为催化剂毒物通常会延迟反应速率，但有时也会抑制可能的副反应，从而导致高选择性的有机转化。 6] 提高催化剂性能的另一种方法是使用碳纳米材料作为载体，因为它们的纳米级受控表面结构导致高度分散的金属纳米粒子固定，具有窄的尺寸分布和高电导率。我们之前报道了碳纳米纤维（CNF）负载的金属纳米粒子在加氢催化剂中的合成和应用。 CNF分为三种类型，其中石墨层是垂直的（片状：CNFP）、平行的（管状：CNF-T）或倾斜堆叠的（人字形：CNF-H）。在这些金属负载的 CNF（M/CNF；M = Ru、Rh、Pd 和 Pt）中，Pt/CNF-P 和 Pt/CNF-H 被证明可作为可重复使用的催化剂，在正辛胺 (OctNH2) 作为催化剂的情况下，以高周转数将卤代硝基苯硝基选择性还原为相应的卤代苯胺。 毒药。由于这些结果，我们对氮掺杂 CNF 作为金属纳米粒子的载体感兴趣。碳纳米结构和氮原子掺杂的结合有望为化学选择性催化反应提供有效的中毒催化剂。在本文中，我们报道了铂纳米颗粒可以固定在氮掺杂的人字形碳纳米纤维（N-CNFH）的表面，形成的Pt/N-CNF-H化合物是功能化硝基芳烃硝基选择性加氢的高效可重复使用催化剂。如先前报道，N-CNF-H 是通过在 MgO 负载的 Ni-Fe 催化剂上使用乙腈和氢气在 530 8C 下进行化学气相沉积来合成的。 N-CNF-H 的元素分析表明，N-CNF-H 中掺入的氮量约为 5 wt%。采用与 Pt/CNF 相同的方法将铂颗粒（金属负载量分别为 1 和 3 wt%）固定在 NCNF-H 上，即在氩气气氛下，在 N-CNF-H 存在下，在甲苯中热分解 [Pt(dba)2]（dba = 二亚苄基丙酮）（方案 1）。
Carbon-supported metal nanoparticles are widely used as sensors, electrocatalysts for fuel cells and Li ion batteries, or heterogeneous catalysts for various organic transformations. Since the catalytic properties of these materials are highly dependent on the supports, numerous studies have been performed to modify the carbon supports to improve their catalyst performances. 2] One method to tailor the chemical and/or physical properties and stabilize metal nanoparticles–support interactions involves the chemical modification of the carbon surface by introduction of functional groups or the doping of heteroatoms. For example, the addition of sulfur, nitrogen, phosphorous, or halogen containing compounds as a catalyst poison to the original catalyst often retards the reaction rate, but sometimes also suppresses possible side reactions, thereby leading to highly selective organic transformations. 6] Another way to improve the catalyst performance is the use of carbon nanomaterials as a support, because their nanolevel controlled surface structures lead to the immobilization of highly dispersed metal nanoparticles with narrow size distributions and high conductivity. We previously reported the synthesis and application of metal nanoparticles supported on carbon nanofibers (CNFs) in hydrogenation catalysts. CNFs are classified into three types, in which the graphite layers are perpendicular (platelet: CNFP), parallel (tubular : CNF-T), or stacked obliquely (herringbone: CNF-H). Among these metal-supported CNFs (M/CNF; M = Ru, Rh, Pd, and Pt), Pt/CNF-P and Pt/CNF-H were proven to act as reusable catalysts for the nitro-selective reduction of halonitrobenzenes to the corresponding haloanilines with high turnover numbers in the presence of n-octylamine (OctNH2) as a catalyst poison. Because of these results, we were interested in nitrogen-doped CNF as a support for metal nanoparticles. The combination of carbon nanostructures and the doping of nitrogen atoms are expected to offer an efficient poisoning catalyst for chemoselective catalytic reactions. In this paper, we report that platinum nanoparticles can be immobilized on the surface of nitrogen-doped, herringbone-type carbon nanofibers (N-CNFH), and the formed Pt/N-CNF-H compounds are highly efficient reusable catalysts for the nitro-selective hydrogenation of functionalized nitroarenes. N-CNF-H was synthesized by using chemical vapor deposition over a MgO supported Ni–Fe catalyst using acetonitrile and hydrogen at 530 8C, as reported previously. Elemental analysis of N-CNF-H revealed the amount of nitrogen incorporated into N-CNF-H to be approximately 5 wt %. Immobilization of platinum particles (metal loadings of ca. 1 and 3 wt %) on NCNF-H was performed by applying the same method as for Pt/ CNF, that is, by thermally decomposing [Pt(dba)2] (dba = dibenzylideneacetone) in toluene in the presence of N-CNF-H under an argon atmosphere (Scheme 1).