Hierarchical flower-like and sphere-like mesoporous γ-Al 2 O 3 microparticles were successfully prepared by a facile hydrothermal method followed by a calcination process using sodium aluminate as aluminum source, urea as precipitating agent, and Pluronic F127 (EO 106 PO 70 EO 106 ), polyacrylic acid sodium (PAAS), and mixed F127–PAAS as structure-directing agents (SDAs), respectively. Effects of the SDAs on the phase structure, morphology, textural properties, surface alkaline, and the adsorption performance toward Cr(VI) and CO 2 of the as-prepared samples were comparatively studied by X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), N 2 adsorption–desorption, CO 2 temperature programmed desorption (CO 2 -TPD), and UV–Vis spectrophotometric method. The results indicate that the sphere-like γ-Al 2 O 3 obtained by using F127 as the SDA shows the best adsorption performance toward Cr(VI) with a high adsorption rate of 95% and adsorption capacity of 5.7mg/g when the adsorption reaches equilibrium for 4h at room temperature. However, the flower-like γ-Al 2 O 3 obtained by using PAAS as the SDA has the biggest CO 2 adsorption capacity of 1.04mmol/g at room temperature. This work provides a simple and practical way to prepare potentially bifunctional γ-Al 2 O 3 adsorbent for the removal of pollutants in water and air treatment from cheap sodium aluminate by using different SDAs.