Size effects of PVP-Pd nanoparticles on the catalytic Suzuki reactions in aqueous solution
Size effects of PVP-Pd nanoparticles on the catalytic Suzuki reactions in aqueous solution
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DOI：
10.1021/la011469q
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发表时间：
2002-06-11
期刊：
影响因子：
3.9
通讯作者：
El-Sayed, MA
中科院分区：
文献类型：
--
作者：
Li, Y;Boone, E;El-Sayed, MA
通过逐步生长反应制备了一系列不同粒径的聚（N-乙烯基-2-吡咯烷酮）（PVP）稳定的Pd纳米颗粒。通过使用平均粒径分别为 3.0、3.9、5.2 和 6.6 nm 的四种 Pd 催化剂，研究了 Pd 粒径对苯基硼酸和碘苯之间的 Suzuki 反应的影响。以初始周转频率（每分钟每摩尔总表面 Pd 原子联苯产物的摩尔数）表示的 Pd 纳米粒子的催化活性按 Pd (3.9 nm) > Pd (3.0 nm) 近似于 Pd (5.2 nm) > Pd (6.6 nm) 的顺序，表明表面 Pd 原子在此反应中并不都具有相同的反应性。催化活性随粒径减小而增加的总体趋势表明，颗粒表面的低配位数顶点和边缘原子是铃木反应的活性位点。最小的 Pd 纳米颗粒的较低催化活性可能是由于反应中间体在颗粒表面上的吸附较强，其中强烈吸附的物质对反应起到毒物的作用，从而降低了反应速率。
A series of poly(N-vinyl-2-pyrrolidone) (PVP)-stabilized Pd nanoparticles with varying particle size are prepared by using the stepwise growth reaction. The effect of Pd particle size on the Suzuki reaction between phenylboronic acid and iodobenzene is investigated by the use of four Pd catalysts with mean particle sizes of 3.0, 3.9, 5.2, and 6.6 nm, respectively. The catalytic activity of the Pd nanoparticles expressed in terms of the initial turnover frequency (moles of the biphenyl product per mole of total surface Pd atoms per min) is found to be in the order of Pd (3.9 nm) > Pd (3.0 nm) approximate to Pd (5.2 nm) > Pd (6.6 nm), indicating that surface Pd atoms do not all have the same reactivity in this reaction. The general trend of increased catalytic activity with the decrease in the particle size suggests that the low-coordination number vertex and edge atoms on the particle surface are active sites for the Suzuki reaction. The lower catalytic activity for the smallest Pd nanoparticles might be due to stronger adsorption of the reaction intermediates on the particle surface, in which the strongly adsorbed species act as a poison to the reaction thereby decreasing the rate of the reaction.