Epitaxially Grown Layered MFI鈥揃ulk MFI Hybrid Zeolitic Materials
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- 作者：Wun-gwi Kim ; Xueyi Zhang ; Jong Suk Lee ; Michael Tsapatsis ; Sankar Nair
- 刊名：ACS Nano
- 出版年：2012
- 出版时间：November 27, 2012
- 年：2012
- 卷：6
- 期：11
- 页码：9978-9988
- 全文大小：950K
- 年卷期：v.6,no.11(November 27, 2012)
- ISSN：1936-086X
文摘
The synthesis of hybrid zeolitic materials with complex micropore鈥搈esopore structures and morphologies is an expanding area of recent interest for a number of applications. Here we report a new type of hybrid zeolite material, composed of a layered zeolite material grown epitaxially on the surface of a bulk zeolite material. Specifically, layered (2-D) MFI sheets were grown on the surface of bulk MFI crystals of different sizes (300 nm and 10 渭m), thereby resulting in a hybrid material containing a unique morphology of interconnected micropores (0.55 nm) and mesopores (3 nm). The structure and morphology of this material, referred to as a 鈥渂ulk MFI鈥搇ayered MFI鈥?(BMLM) material, was elucidated by a combination of XRD, TEM, HRTEM, SEM, TGA, and N2 physisorption techniques. It is conclusively shown that epitaxial growth of the 2-D layered MFI sheets occurs in at least two principal crystallographic directions of the bulk MFI crystal and possibly in the third direction as well. The BMLM material combines the properties of bulk MFI (micropore network and mechanical support) and 2-D layered MFI (large surface roughness, external surface area, and mesoporosity). As an example of the uses of the BMLM material, it was incorporated into a polyimide and fabricated into a composite membrane with enhanced permeability for CO2 and good CO2/CH4 selectivity for gas separations. SEM-EDX imaging and composition analysis showed that the polyimide and the BMLM interpenetrate into each other, thereby forming a well-adhered polymer/particle microstructure, in contrast with the defective interfacial microstructure obtained using bare MFI particles. Analysis of the gas permeation data with the modified Maxwell model also allows the estimation of the effective volume of the BMLM particles, as well as the CO2 and CH4 gas permeabilities of the interpenetrated layer at the BMLM/polyimide interface.