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

Abstract

Herein, mesoporous ZnAl2O4 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 ZnAl2O4 nanoflakes with the thickness of ∼20 nm were composed of numerous nanoparticles, which resulted in a high specific surface area of 245 m2 g-1. The formation mechanism of the ZnAl2O4 nanoflakes was comprehensively investigated, and the results showed that a 2D growth process of the Zn6Al2(OH)16(CO3)·4H2O crystallites with the assistance of [bdmim][Cl] was the key for the induction of ZnAl2O4 nanoflakes. Moreover, mesopores were formed between adjacent nanoparticles due to the release of CO2 and H2O molecules from Zn6Al2(OH)16(CO3)·4H2O during the calcination process.