Mesoporous MgO adsorbents with diverse basic sites were prepared via a urea hydrolysis synthesis method for CO2 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 CO2. Furthermore, the main component of adsorbed CO2 surface species swings from bicarbonate to bidentate and unidentate carbonates with increase of adsorption temperature. The highest CO2 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 degrees 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 CO2 capture, with a nearly 20-fold enhancement of the commercialized light MgO. Additionally, the results of CO2 uptake studied under diluted and wet (H2O containing) CO2 conditions for the as-prepared MgO adsorbent also suggested good prospect in practical applications.