Aggregation-Free Gold Nanoparticles in Ordered Mesoporous Carbons: Toward Highly Active and Stable Heterogeneous Catalysts

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• 作者：Shuai Wang ; Qingfei Zhao ; Huimin Wei ; Jian-Qiang Wang ; Minhyung Cho ; Hae Sung Cho ; Osamu Terasaki ; Ying Wan
• 刊名：The Journal of the American Chemical Society
• 出版年：2013
• 出版时间：August 14, 2013
• 年：2013
• 卷：135
• 期：32
• 页码：11849-11860
• 全文大小：612K
• 年卷期：v.135,no.32(August 14, 2013)
• ISSN：1520-5126

文摘

A coordination-assisted synthetic approach is reported here for the synthesis of highly active and stable gold nanoparticle catalysts in ordered mesoporous carbon materials using triblock copolymer F127 as a structure-directing agent, thiol-containing silane as a coordination agent, HAuCl₄ as a gold source, and phenolic resin as a carbon source. Upon carbonization, the gold precursor becomes reduced to form monodispersed Au nanoparticles of ca. 9.0 nm, which are entrapped or confined by the 鈥渞igid鈥?mesoporous carbonaceous framework. Nanoparticle aggregation is inhibited even at a high temperature of 600 掳C. After removal of the silica component, the materials possess the ordered mesostructure, high surface area (1800 m²/g), large pore volume (1.19 cm³/g), and uniform bimodal mesopore size (<2.0 and 4.0 nm). The monodispersed gold nanoparticles are highly exposed because of the interpenetrated bimodal pores in the carbon framework, which exhibit excellent catalytic performance. A completely selective conversion of benzyl alcohol in water to benzoic acid can be achieved at 90 掳C and 1 MPa oxygen. Benzyl alcohol can also be quantitatively converted to benzoic acid at 60 掳C even under an atmospheric pressure, showing great advantages in green chemistry. The catalysts are stable, poison resistant, and reusable with little activity loss due to metal leaching. The silane coupling agent played several functions in this approach: (1) coordinating with gold species by the thiol group to benefit formation of monodispersed Au nanoparticles; (2) reacting with phenolic resins by silanol groups to form relatively 鈥渞igid鈥?composite framework; (3) pore-forming agent to generate secondary pores in carbon pore walls, which lead to higher surface area, larger pore volumes, and higher accessibility to to the gold nanoparticles. Complete removal of the silica component proves to have little effect on the catalytic performance of entrapped Au nanoparticles.