Unusual morphology transformation and basicity of magnesium oxide controlled by ageing conditions and its carbon dioxide adsorption

The physicochemical changes of magnesium oxide (MgO) by different preparation methods have been extensively explored for various applications; however, few studies have been conducted on the morphology and physicochemical properties of MgO controlled by various ageing conditions even though an ageing step is one of the important steps in the precipitation. In this study, morphological transformation of MgO was achieved by controlling the ageing time at different temperatures and the unusual transformation was observed; Microsphere-structured MgO, known to be unstable at low temperatures, could be formed even at 25 °C, owing to the abundant amount of OH^-. In addition, the surface basicity was significantly affected by the aging conditions. Ageing at 60 °C furnished stronger basic sites on MgO, which resulted from the abundant oxygen vacancies. Notably, an unusual peak in the sample prepared at 80 °C of aging temperature was observed at 656 °C in the CO₂temperature-programmed desorption profile, and it was attributed to the desorption of strongly adsorbed hydroxyl groups. The surface area was maximized (350 m²g^-1) by employing the ageing temperature of 80 °C, and the CO₂sorption capacities of as-prepared samples were 6-7 wt.% during adsorption for 120 min at 25 °C. Understanding the physicochemical properties and basicity of MgO can facilitate the design of adsorbents or catalysts as a platform material.