A template-free, thermal decomposition method to synthesize mesoporous MgO with a nanocrystalline framework and its application in carbon dioxide adsorption

Abstract

Alkaline earth-based oxides are important materials in the storage of carbon dioxide. Here we present a template-free synthesis method for mesoporous magnesium oxide (MgO) via the thermal decomposition of anhydrous magnesium acetate. Characterization of the crystalline phase, particle size, pore size and surface area for mesoporous MgO samples was accomplished using a variety of techniques and methods including scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), powder X-ray diffraction (XRD), and nitrogen adsorption analysis. The results showed that mesoporous MgO prepared from anhydrous magnesium acetate had a high surface area in the range of 120–136 m² g⁻¹ and a narrow pore size distribution in the range of 3–4 nm. The pore structure was composed of small primary MgO nanoparticle aggregates with interparticle connections. In situ transmission FTIR spectroscopy was used to investigate CO₂ adsorption on mesoporous MgO. This spectroscopic investigation showed that mesoporous MgO exhibited enhanced CO₂ adsorption capacity relative to commercially available MgO nanoparticles. This difference was attributed mainly to an increase in surface area. Differences in surface carbonate/bicarbonate speciation were observed between the mesoporous and commercial MgO samples and were related to structural differences for the smaller nanoparticles.