2D Zeolite Coatings: Langmuir–Schaefer Deposition of 3 nm Thick MFI Zeolite Nanosheets

Abstract

Stable suspensions of zeolite nanosheets (3 nm thick MFI layers) were prepared in ethanol following acid treatment, which partially removed the associated organic structure-directing agent. Nanosheets from these suspensions could then be dispersed at the air-water interface and transferred to silicon wafers using Langmuir-Schaefer deposition. Using layer-by-layer deposition, control on coating thickness was demonstrated. In-plane X-ray diffraction (XRD) revealed that the deposited nanosheets contract upon calcination similar to bulk MFI crystals. Different methods for secondary growth resulted in preferentially oriented thin films of MFI, which had sub-12-nm thickness in certain cases. Upon calcination, there was no contraction detectable by in-plane XRD, indicating well-intergrown MFI films that are strongly attached to the substrate.

Nanoscale Control of Homoepitaxial Growth on a Two‐Dimensional Zeolite

“…The sample shown in Figure Figure 2 d, confirming that TEAOH-grown films are b-oriented, in contrast to the a-and b-oriented films using TPAOH-based sols ( Figure S4). [22] In addition to lateral growth, thickening and appearance of steps on the previously flat nanosheet surfaces are evident (Figures 3 a,b). Although in-plane Bragg peaks for the coatings of 2D-MFI nanosheets shift upon calcination (indicating a contraction of the in-plane crystallographic dimensions), peak positions for the TEAOH-grown films exhibit no shift upon calcination due to strong attachment to other nanosheets and the support.…”

“…[22] They were then calcined in air at 500 8C to remove the occluded structure directing agent (SDA, C 22 H 45 -N + (CH 3 ) 2 -C 6 H 12 -N + (CH 3 ) 2 -C 6 H 13 ·2 OH À . [22] It was then attempted to grow these SDA-free Si-supported nanosheets wider, eventually causing them to laterally intergrow, while minimizing increase in thickness and nonoriented growth (owing to rotational and random intergrowths). [22] It was then attempted to grow these SDA-free Si-supported nanosheets wider, eventually causing them to laterally intergrow, while minimizing increase in thickness and nonoriented growth (owing to rotational and random intergrowths).…”

Zeolite membranes – a review and comparison with MOFs

“…6 Further, secondary growth of these seed layers has advanced through novel methods such as gel-free growth 7 and minimization of twinning. 8 These and other developments have enabled the formation of sub-1 mm zeolite membranes.…”

para‐Xylene Ultra‐selective Zeolite MFI Membranes Fabricated from Nanosheet Monolayers at the Air–Water Interface

“…It has been demonstrated that zeolite, [32,33] zeolite nanosheet, [34] MOF, [35] graphene, [36] and graphene oxide [37] monolayers can be formed at an air-water interface from where they can be transferred to non-porous substrates as oriented and well-packed coatings.H owever,d eposition on porous supports for high-performance separation membrane has not yet been reported. Herein, we demonstrate asimple approach by which monolayers of directly-synthesized MFI nanosheets can be transferred from the air-water interface onto aporous support.…”

“…Previous studies have shown that MFI nanosheets can form dense and uniform monolayers at the air-water interface, [34] which are highly desired as seed coatings for films or membranes.The directly synthesized MFI nanosheets used herein are water-compatible and do not require any postsynthesis treatment (e.g., the acid treatment required by exfoliated nanosheets [34] )tobedispersed in water. Previous studies have shown that MFI nanosheets can form dense and uniform monolayers at the air-water interface, [34] which are highly desired as seed coatings for films or membranes.The directly synthesized MFI nanosheets used herein are water-compatible and do not require any postsynthesis treatment (e.g., the acid treatment required by exfoliated nanosheets [34] )tobedispersed in water.…”