Yolk鈥揝hell Nanocrystal@ZIF-8 Nanostructures for Gas-Phase Heterogeneous Catalysis with Selectivity Control
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- 作者：Chun-Hong Kuo ; Yang Tang ; Lien-Yang Chou ; Brian T. Sneed ; Casey N. Brodsky ; Zipeng Zhao ; Chia-Kuang Tsung
- 刊名：The Journal of the American Chemical Society
- 出版年：2012
- 出版时间：September 5, 2012
- 年：2012
- 卷：134
- 期：35
- 页码：14345-14348
- 全文大小：269K
- 年卷期：v.134,no.35(September 5, 2012)
- ISSN：1520-5126
文摘
A general synthetic strategy for yolk鈥搒hell nanocrystal@ZIF-8 nanostructures has been developed. The yolk鈥搒hell nanostructures possess the functions of nanoparticle cores, microporous shells, and a cavity in between, which offer great potential in heterogeneous catalysis. The synthetic strategy involved first coating the nanocrystal cores with a layer of Cu2O as the sacrificial template and then a layer of polycrystalline ZIF-8. The clean Cu2O surface assists in the formation of the ZIF-8 coating layer and is etched off spontaneously and simultaneously during this process. The yolk鈥搒hell nanostructures were characterized by transmission electron microscopy, scanning electron microscopy, X-ray diffraction, and nitrogen adsorption. To study the catalytic behavior, hydrogenations of ethylene, cyclohexene, and cyclooctene as model reactions were carried out over the Pd@ZIF-8 catalysts. The microporous ZIF-8 shell provides excellent molecular-size selectivity. The results show high activity for the ethylene and cyclohexene hydrogenations but not in the cyclooctene hydrogenation. Different activation energies for cyclohexene hydrogenation were obtained for nanostructures with and without the cavity in between the core and the shell. This demonstrates the importance of controlling the cavity because of its influence on the catalysis.