Calcination-free fabrication of highly b-oriented silicalite-1 (S-1) zeolite films in the absence of organic structure-directing agents (OSDAs) is attractive but still challenging. Herein, for the first time, we show a novel route for calcination-free synthesis of a b-oriented S-1 zeolite film in the absence of OSDAs. The key to this success is a rational secondary growth of zeolite crystals on the surface of supports by avoidance of the formation of zeolite nuclei in the system due to the absence of OSDAs. Because of OSDA-free synthesis of S-1, it not only reduces the cost of zeolite films but also avoids the calcination of OSDAs in the synthesis, thus avoiding the formation of cracks in the zeolite films. In addition, the calcination-free fabrication is favorable for reduction of zeolite film defects such as a terminal OH group. As a result, the zeolite films obtained from this work exhibit higher hydrophobicity than the conventional one. Furthermore, the current polarization curve of this S-1 zeolite film shows excellent corrosion resistance. The aforementioned features would be potentially important for industrial application of zeolite films in the near future.
Zeolitic imidazolate framework 8 (ZIF-8) is effective for C3H6/C3H8 separation because of the “sieving effect” of a six-membered (6-M) window. Here, we demonstrate that ZIF-8 is a versatile material that could effectively separate C2H4 from C2H6 via its 4-M window along the <100> direction. We established a facile and environmentally friendly carbon nanotube (CNT)–induced oriented membrane (CNT-OM) approach to fabricate a {100}-oriented ZIF-8 membrane (100-M). In this approach, 2-methyimidazole was anchored onto the CNT surface followed by 3-hour in situ growth in aqueous solution at room temperature. The obtained 100-M, whose 4-M window is aligned along the transport pathway, showed ~3 times higher C2H4/C2H6 selectivity than a randomly oriented membrane. Thus, this work demonstrates that the membrane orientation plays an important role in tuning selectivity toward different gas pairs. Furthermore, 100-M exhibited excellent mechanical stability that could sustain the separation performance after bending at a curvature of ~109 m−1.
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