Preparation of mesoporous ZnAl 2 O 4 nanoflakes by ion exchange from a Na-dawsonite parent material in the presence of an ionic liquid.

Herein, mesoporous ZnAl 2 O 4 spinel nanoflakes were prepared by an ion-exchange method from a Na-dawsonite parent material in the presence of an ionic liquid, 1-butyl-2,3-dimethylimidazolium chloride ([bdmim][Cl]), followed by calcination at 700 °C for 2 h. The as-obtained products were characterized by several techniques such as X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy dispersive X-ray spectroscopy (EDX). The ZnAl 2 O 4 nanoflakes with the thickness of ∼20 nm were composed of numerous nanoparticles, which resulted in a high specific surface area of 245 m 2 g -1 . The formation mechanism of the ZnAl 2 O 4 nanoflakes was comprehensively investigated, and the results showed that a 2D growth process of the Zn 6 Al 2 (OH) 16 (CO 3 )·4H 2 O crystallites with the assistance of [bdmim][Cl] was the key for the induction of ZnAl 2 O 4 nanoflakes. Moreover, mesopores were formed between adjacent nanoparticles due to the release of CO 2 and H 2 O molecules from Zn 6 Al 2 (OH) 16 (CO 3 )·4H 2 O during the calcination process.