Crystal Facets Make a Profound Difference in Polyoxometalate-Containing Metal鈥揙rganic Frameworks as Catalysts for Biodiesel Production

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• 作者：Yiwei Liu ; Shumei Liu ; Danfeng He ; Ning Li ; Yujuan Ji ; Zhiping Zheng ; Fang Luo ; Shuxia Liu ; Zhan Shi ; Changwen Hu
• 刊名：Journal of the American Chemical Society
• 出版年：2015
• 出版时间：October 7, 2015
• 年：2015
• 卷：137
• 期：39
• 页码：12697-12703
• 全文大小：436K
• ISSN：1520-5126

文摘

An inherent challenge in using metal鈥搊rganic frameworks (MOFs) for catalysis is how to access the catalytic sites generally confined inside the porous structure, in particular for substrates larger than the pores. We present here a promising solution to bypass this roadblock by modulating the facets of a crystalline MOF NENU-3a to enhance the facet exposure of the catalytic sites and the adsorption of substrates. Specifically, by transforming it with encapsulated catalysis-responsible polyoxometalate from octahedron characterized entirely by {111} facets to cube with only {100} facets, much enhanced catalytic activities were observed, especially for sterically demanding substrates that are otherwise hard to diffuse into the pores. Crystallographic analysis and adsorption/desorption experiments collectively established the critical effects of morphological control on the enhanced catalysis. The cubic crystals were then applied for biodiesel production, reaching more than 90% conversion of fatty acids (C₁₂鈥揅₂₂) in comparison to <22% using octahedral crystals.