(713e) Efficient Gas Sieving from Assembled Films of Nanoporous Zeolitic and Carbon Nitride Nanosheets
An innovative route for the fabrication of the gas separation membrane is to synthesize nanoporous two-dimensional (n2d) nanosheets hosting size-sieving nanopores . Subsequently, n2d can be self-assembled leading to thin yet permselective membranes, improving the scalability of nanoporous membranes. However, barring metal-organic frameworks nanosheets , this has not been demonstrated. In this presentation, I will report two examples of the top-down synthesis of n2d materials (sodalite precursor RUB-15  and polytriazine imide or PTI ) hosting crystalline nanoporous structures for sieving of H2 from CO2, N2 and CH4, as confirmed by our ab-initio molecular simulations. Highly crystalline layers were synthesized using optimized hydrothermal and solid-state synthesis routes for RUB-15 and PTI, respectively, leading to high-aspect-ratio layered plates. Exfoliation of these nanosheets into highly crystalline (as confirmed by high-resolution transmission electron microscopy) and predominantly single-layer nanosheets (as confirmed by atomic force microscopy) was achieved using swelling of the layers, melt compounding, and by the intercalation of solvents. Finally, packing of these nanosheets into compact films by self-assembly produced molecular-sieving membranes with attractive gas-sieving performances. For example, zeolite nanosheet membranes yielded H2/CO2, H2/N2 and H2/CH4 selectivities of 13, 93.7 and 116.6, respectively, while the PTI nanosheets membranes yielded H2/CH4 and H2/N2 selectivities of 41 and 93, respectively. Overall, the synthesis of molecular-sieving membranes by the colloidal self-assembly can address the scale-up issues related to the inorganic membranes.
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