Controlled synthesis of MgO with diverse basic sites and its CO 2 capture mechanism under different adsorption conditions

Abstract Mesoporous MgO adsorbents with diverse basic sites were prepared via a urea hydrolysis synthesis method for CO 2 capture. With elevated hydrolysis temperatures, the phase transition process made great contributions to the morphological changes of the precursor architectures. In situ DRIFTS analysis demonstrated that various carbonate surface species including bicarbonate, bidentate, and unidentate carbonates were formed on the obtained MgO during interaction with CO 2 . Furthermore, the main component of adsorbed CO 2 surface species swings from bicarbonate to bidentate and unidentate carbonates with increase of adsorption temperature. The highest CO 2 uptake of 1.22–1.99 mmol g −1 was attained for MgO sample at the lowest calcination temperature in a wide temperature range of 60–300 °C. High specific surface area (372.0 m 2  g −1 ), large pore volume (0.38 cm 3  g −1 ) as well as diverse basic sites of the synthesized MgO make it an eligible candidate for CO 2 capture, with a nearly 20-fold enhancement of the commercialized light MgO. Additionally, the results of CO 2 uptake studied under diluted and wet (H 2 O containing) CO 2 conditions for the as-prepared MgO adsorbent also suggested good prospect in practical applications.