Nanotechnologies / Materials
Electronics, Catalysis, Sensing

Nanosheet synthesis using liquid crystals as templates
Department of Materials Engineering Science, Graduate School of Engineering Science
Associate Professor Yoshiaki Uchidahttps://researchmap.jp/Yoshiaki_Uchida?lang=en

Abstract

Nanotechnologies / Materials

We have synthesized unprecedented amorphous aluminosilicate
nanosheets by the Two-dimensional Reactor in Amphiphilic Phase(TRAP) method, which we proposed as a new nanosheet synthesis method using liquid crystals. Four types of zeolite nanosheets
could be converted from a single type of amorphous aluminosilicate nanosheet by the Dry Gel Conversion (DGC) method using
Structure-Directing Agent (SDA). Cracking tests of low-density polyethylene (LDPE) catalyzed by one of the zeolite nanosheets, CHAtype zeolite nanosheets, showed that the ratio of lower olefins washigher than that of conventional CHA-type zeolite crystals.

as methanol-olefin catalysts, polymer degradation, and separation
membranes.
The MFI and CHA types in this study are commonly used as catalysts; MFI-type zeolite nanosheets have been reported in anothernanosheet synthesis methods, but this is the first report on the CHAtype.
This method has another advantage; it is easy to scale up thismethod due to the use of self-assembly as templates and the low
cost of the amphiphilic molecules.

▍ Background & Results
Nanostructured materials show shape-derived properties. Nanosheets are so thin that they are highly dispersible and exhibit
nanosize effects, and they are easy to handle thanks to their width,
which is more than 100 times greater than their thickness. Nanosheet synthesis by top-down exfoliation, a method commonly usedin the past, cannot synthesize nanosheets of non-exfoliated materials. Therefore, bottom-up methods by anisotropic growth using
various interfaces as templates have been investigated. A synthesis method that can be scaled up for practical use and that allows
control of nanosheet size at low cost is required. The authors haverecently developed a nanosheet synthesis method using liquid
crystals as templates (TRAP method).
Here, we proposed a new method to synthesize amorphousaluminosilicate nanosheets using the TRAP method and to convert
them into various types of zeolite nanosheets by DGC. Four typesof zeolite nanosheets were obtained from the same amorphous aluminosilicate.
First, amorphous aluminosilicate nanosheets were synthesizedusing hydrophilic TRAPs in the HL phase of decane solutions ofionic amphiphilic molecules. The raw materials were tetraethyl orthosilicate and aluminum isopropoxide. The resulting powder wasan amorphous aluminosilicate nanosheet with a thickness of 1.96
± 0.67 nm and a width of 395 ± 137 nm.
The amorphous aluminosilicate nanosheets were then immersedin an aqueous solution of SDA and dried to form a gel. Crystallization in a steam at 160℃, we obtained four types of zeolite nanosheets (PHI, CHA, SOD, and MFI types) by changing the structure-defining agent.
Furthermore, we confirmed that the CHA-type zeolite nanosheets
work as the catalyst of cracking of low-density polyethylene (LDPE).
The ratio of lower olefins was better than conventional CHA-typezeolite crystals.

▍ Significance of the research and Future perspective
The methodology of this study is applicable to many types ofzeolites. Due to their thickness and large external surface area, zeolite nanosheets have great potential for various applications such

P a t e n t JP7290230, JP6978783
Sasaki, Koki; Uchida, Yoshiaki; Nishiyama, Norikazu. Bottom-up synthesis of nanosheets at various interfaces. ChemPlusChem. 2023, 88 (10),e202300255. doi: 10.1002/cplu.202300255
Sasaki, Koki; Uchida, Yoshiaki; Nishiyama, Norikazu et al. Amorphous aluminosilicate nanosheets as universal precursors for the synthesis of diverse
Tr e a t i s ezeolite nanosheets for polymer-cracking reactions. Angewandte Chemie International Edition. 2022, 61 (46), e202213773. doi: 10.1002/anie.202213773
Uchida, Yoshiaki; Nishizawa, Takuma; Nishiyama, Norikazu et al. Nanosheet formation in hyperswollen lyotropic lamellar phases. Journal of the American
Chemical Society. 2016, 138 (4), 1103-1105. doi: 10.1021/jacs.5b11256
UR
L http://www.cheng.es.osaka-u.ac.jp/nishiyamalabo/english/research/359/3141.html
K e y w o r d aluminosilicate, lamellar phase, nanosheets, zeolite, catalysts