The synthesis of hybrid zeolitic materials with complex micropore-mesopore 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 μm), 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 "bulk MFI-layered MFI" (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. © 2012 American Chemical Society.
|Original language||English (US)|
|Number of pages||11|
|State||Published - Oct 18 2012|
Bibliographical noteKAUST Repository Item: Exported on 2020-10-01
Acknowledged KAUST grant number(s): KUS-I1-011-21
Acknowledgements: This publication is based on work supported by Award No. KUS-I1-011-21, made by King Abdullah University of Science and Technology (KAUST). M.T. and X.Z. acknowledge support from the Catalysis Center for Energy Innovation (award DESC00001004), an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences. Portions of this work were conducted at the University of Minnesota Characterization Facility, which receives partial support from the National Science Foundation through the NNIN program. We also thank Prof. W. J. Koros (Georgia Tech) for helpful discussions and for proofreading the manuscript.
This publication acknowledges KAUST support, but has no KAUST affiliated authors.