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再谈石峰博士的纳米金研究
 
作者：深秋十月
 
石峰博士的纳米金研究始于2002年的一篇报道[1]。他将某种离子交换树脂与
HAuCl4溶液反应并烘干后，发现得到的是纳米金，认为在载金树脂的制备过程
中发生了还原。但他对发生还原的原因未作任何解释，也未作任何对照实验以
说明这种未知原因对实验结果的影响。
 
石峰发表的两篇报道[1,2]在纳米金的制备上存在一个共同的问题，即具有催
化活性的载金树脂呈碱性，能够促进二氧化碳的反应。经氢氧化钠处理的季铵
盐型离子交换树脂表面带有碱性的氢氧化季铵盐(R4N+OH-)。在与HAuCl4反应
时，尽管树脂表面过量的OH-可能与AuCl4-继续反应生成氢氧化物而被消耗，
但在载金量较小时，树脂表面应仍有碱存在。在排除这一可能之前，两篇报道
的结论均不能成立。
 
另外，在石峰等的纳米金研究中还可能存在另一个问题，即实验使用的离子交
换树脂在催化剂制备和使用中的高温下可能发生分解。已知氢氧化季铵盐在加
热条件下会发生霍夫曼降解[3，4]，生成水，烯烃和三级胺。因此，加热前后
的树脂表面可能有相当大的差异。三级胺和氢氧化季铵盐一样呈碱性，能够促
进二氧化碳的反应。
 
综上所述，石峰等在实验方案设计上存在重大疏漏，得到的实验结果不足以支
持其结论。

[1] Shi, F. et al, J. Catal. 2002, 211, 548
 
Several polymer-immobilized Au catalysts (or Pd catalysts for the purpose 
of comparison) were prepared as follows. Au/poly1 consisted of dried 
polymer pellets (ca. φ =0.5 mm, Ionexchanger IV, Merck) without any 
pretreatment which were impregnated with 0.004 M aqueous solution of 
HAuCl4·4H2O and then dried at 60?C for 3 h. Au/poly2 consisted of 
dried polymer which was pretreated with NaOH, and then the same 
preparation procedure as for Au/poly1 was followed. Au/poly3 was 
prepared using the same procedure as for Au/poly2 except that a 0.004 M 
solution of HAuCl4·4H2O+acetone was used. The catalyst pellets could 
be dried more easily at room temperature using acetone as solvent. 
Au/poly4 and 5 were prepared using the same preparation procedure as 
for Au/poly3 except that 0.002 M and 0.001 M solutions of HAuCl4·4H2O
+acetone were used respectively. Au-K/poly was prepared using the same 
procedure asAu/poly3 but KOH was used instead of NaOH. Pd/poly1 and 
2 were prepared using the same procedure as for Au/poly2, but 
HAuCl4·4H2O was replaced with H2PdCl4 or Pd(phen)2Cl2 (phen: 1,10-
phenanthroline monohydrate), respectively. The basic properties of 
polymerimmobilized Au catalysts are summarized in Table 1. Only small 
BET surface areas (Micromeritics ASAP 2010 instrument) for the polymer-
immobilized Au catalysts were found. Catalysts with differentAu loadings 
(3520 ICPAES) were obtained, and high Na contents in Au/poly2–5, were
observed. XPS analysis (VG ESCALAB 210) was conducted over the 
polymer-immobilized Au catalysts. The results showed Au+1 in Au/poly1 
but Au0 in Au/poly2–5 and Au-K/poly. No Au+3 species on the polymer 
could be observed in these catalysts, indicating that redution of Au+3 
species occurred during catalyst preparation. TEM (JEOL JEM-1200EX) 
images of Au/poly3 confirmed that the average size of the Au particles 
was less than 10 nm (Fig. 1).

[2] Shi, F. et al, J. Am. Chem. Soc. 2005, 127, 4182; Supporting
Information
 
Preparation of Au/poly: polymer immobilized Au catalysts, Au/poly, was
prepared as follows: 2g of dried polymers (ca. φ0.5 mm, Amberlite IRA-
400 (poly1), Shandong Dongda Chemical Industry Company, Zibo, 255200, 
China) was pretreated with 2M NaOH solution for 6 hours, and then 
filtrated and washed by distilled waster for 3 times (10ml×3). After 
drying at 80  for 3 hours, the ionexchanger was dipped in 0.001~0.006M 
solution of HAuCl4?4H2O and dried at 150  for 6 hours, and polymer 
supported nano-gold catalysts named 0.01wt%Au/Poly1, 0.05wt%Au/Poly1, 
0.1wt%Au/Poly1 and 0.5wt%Au/Poly1 were obtained. The gold contents 
were 0.01wt%, 0.05wt%, 0.1wt% and 0.5wt% respectively. Using Amberlite 
IR-120 (poly 2) to instead of poly1, another catalyst named 
0.05wt%Au/Poly2 was prepared. It was worth to note that the procedure 
for preparation of the catalysts had great effect on the catalytic 
activity and some unclear factors usually affected the catalytic 
activity severely. 
 
[3] Mayr, H. et al, Euro. J. Org. Chem. 2000, 11, 2013
 
Hofmann Degradation of 3b-I and 3h-I According to Ref.:[7] 1,2,5,6-
Tetrahydropyridinium iodide 3b-I or 3h-I was heated under reflux in 
aqueous NaOH solution for 40 h. Thereafter, the organic layer was 
separated, and the aqueous layer was extracted with diethyl ether. The 
combined organic phases were dried with Na2SO4. The solvent was 
removed in vacuo and the oily residue was distilled under reduced 
pressure to yield the tertiary amines 5 and 6 as liquids.
 
[4] Kini, S. V. et al, Tetrahedron Lett. 2004, 45, 4171
 
Compounds 1a–e were converted to the corresponding 1-arylmethyl-1,2,3,
4-tetrahydro-2,2-dimethylisoquinolinium iodides6 2a–e by refluxing 
with CH3I and acetone for 8 h. These quaternary ammonium salts on 
refluxing with methanolic KOH underwent Hofmann elimination6 and gave 
stilbenes 3a–e.

(XYS20051224)

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