Solvent-Free Secondary Growth of Highly b-Oriented MFI Zeolite Films from Anhydrous Synthetic Powder

Abstract

Up to date, zeolite films have been mainly fabricated by in situ crystallization, secondary growth in a solution/hydrogel, or occasionally by vapor phase transformation of dry gel. Here we demonstrate for the first time a solvent-free secondary growth method for b-oriented silica MFI zeolite films using the synthetic powder from ground anhydrous raw solids in the presence of NH4F. Typically, precisely b-oriented MFI zeolite films are synthesized from seed layers of highly b-oriented MFI zeolite crystals in the synthetic powder of 1SiO2:0.035TPABr:0.05NH4F at 175 °C for 6 h. If needed, b-oriented MFI zeolite multilayer films can be acquired by changing the synthesis time or the amount of NH4F in the synthetic powder. Compared with the traditional hydrothermal synthesis, the approach developed here may provide a new avenue for fabricating high quality zeolite films/membranes.

Uniform hierarchical MFI nanosheets prepared via anisotropic etching for solution-based sub–100-nm-thick oriented MFI layer fabrication

“…In contrast, developing facile synthetic methods enabling precise control over layer thickness remained largely unexplored. It has been reported that twin-free b-oriented MFI layers with sub-100-nm thickness could be obtained by using the dry gel conversion (20,36) or gel-less method (24,37); nevertheless, it was unclear whether the commonly used solution-based epitaxial growth method could be used for fabricating sub-100-nm-thick b-oriented MFI layers.…”

Single‐Mode Microwave Heating‐Induced Concurrent Out‐of‐Plane Twin Growth Suppression and In‐Plane Epitaxial Growth Promotion of b‐Oriented MFI Film under Mild Reaction Conditions

“…Recent decades have witnessed great efforts on the preparation of b ‐oriented MFI films with few twins . Diverse methods like multi‐mode microwave heating, precursor solution pretreatment, employing specifically designed template ( trimer ‐TPAOH), vapor phase transformation, solvent‐free epitaxial growth and additive addition (like ammonia salts, sodium tungstate and 1,2‐dihydroxybenzene) have proven effective for twin suppression.…”

Anisotropic Gas Separation in Oriented ZIF‐95 Membranes Prepared by Vapor‐Assisted In‐Plane Epitaxial Growth

“…Normally, oriented membranes display superior separation performances in comparison with randomly oriented ones because a perfect orientation often results in a reduction of intercrystalline defects and transport pathways, which is helpful to enhance the selectivity and permeance. Therefore, much effort has been paid on the preparation of oriented molecular sieve membranes [25–34] …”

“…Further, it should be noted that the presence of synthesis building blocks (Zn 2+ and cbIM) in the colloidal suspension of ZIF‐95 seeds is necessary for the formation of a dense ZIF‐95 membrane through epitaxial growth. As shown in Figure S12, the ZIF‐95 seed crystals can still grow together and then form a rather continuous and oriented ZIF‐95 membrane layer through vapor‐assisted in‐plane epitaxial growth, but observable gaps still exist if the synthesis building blocks Zn 2+ and cbIM were not added to the colloidal suspension of the ZIF‐95 seeds during vacuum filtration, which can be attributed to an insufficient concentration of precursor nutrients for secondary growth for a dense ZIF‐95 membrane [34] …”