Synthesis, Characterization, and CO2 Adsorptive Behavior of Mesoporous AlOOH‐Supported Layered Hydroxides

Abstract A novel CO 2 solid sorbent was prepared by synthesizing and modifying AlOOH‐supported CaAl layered double hydroxides (CaAl LDHs), which were prepared by using mesoporous alumina (γ‐Al 2 O 3 ) and calcium chloride (CaCl 2 ) in a hydrothermal urea reaction. The nanostructured CaAl LDHs with nanosized platelets (3–30 nm) formed and dispersed inside the crystalline framework of mesoporous AlOOH (boehmite). By calcination of AlOOH‐supported LDHs at 700 °C, the mesoporous CaAl metal oxides exhibited ordered hexagonal mesoporous arrays or uniform nanotubes with a large surface area of 273 m 2 g −1 , a narrow pore size distribution of 6.2 nm, and highly crystalline frameworks. The crystal structure of the calcined mesoporous CaAl metal oxides was multiphasic, consisting of CaO/Ca(OH) 2 , Al 2 O 3 , and CaAlO mixed oxides. The mesoporous metal oxides were used as a solid sorbent for CO 2 adsorption at high temperatures and displayed a maximum CO 2 capture capacity (≈45 wt %) of the sorbent at 650 °C. Furthermore, it was demonstrated that the mesoporous CaAl oxides showed a more rapid adsorption rate (for 1–2 min) and longer cycle life (weight change retention: 80 % for 30 cycles) of the sorbent because of the greater surface area and increased number of activated sites in the mesostructures. A simple model for the formation mechanism of mesoporous metal oxides is tentatively proposed to account for the synergetic effect of CaAl LDHs on the adsorption of CO 2 at high temperature.