This study investigates the effect of core-shell-structured supports prepared with alumina as the core on the CO2 capture performance of K2CO3. One main issue in using alumina-based-supported K2CO3 is the high moisture uptake of the sorbent, which converts active sites of K2CO3 to hydrated byproducts with a very low CO2 capture capacity. To address this issue, the support was shelled with a less hydrophilic material using a core-shell technique. Six core-shell-structured supports were prepared using alumina-based cores (gamma-alumina and boehmite), and TiO2, ZrO2, and SiO2 shells. K2CO3 was impregnated on each support and tested in a thermogravimetric analyzer over ten cycles. K2CO3/boehmite/TiO2 showed the lowest moisture uptake and the highest surface area, and thus the best CO2 capture performance. A semiempirical model was developed using a response surface methodology to optimize the CO2 capture capacity of K2CO3/boehmite/TiO2. The optimal amounts of the operating parameters including carbonation temperature, carbonation time, and H2O-to-CO2 flow rate ratio, were 61 degrees C, 40 min, and 1.15, respectively. The maximum CO2 capture capacity at the optimal point was 6.61 mmol CO2/g K2CO3, which is equal to 92% of the theoretical value. Therefore, the use of K2CO3/boehmite/TiO2 at the obtained optimal condition is proposed as a suitable option for postcombustion processes.