Preparation of mesoporous ZnAl2O4 nanoflakes by ion exchange from a Na-dawsonite parent material in the presence of an ionic liquid

摘要

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.