The CO2 capture performance of amine-functionalized solid adsorbents highly relies on the structure of the porous supports. Here, we present a facile melamine based approach for the synthesis of hierarchical architecture composed of ultrathin mesoporous silica nanosheets. The synthesized silica nanosheets possess a surface area of 463.5 cm2 g−1 and pore volume of 1.3 cm3 g−1 with capability for loading large amount of amines. After impregnated with 50 wt% polyethyleneimine, the nanosheets based composite showed higher CO2 capture ability (176.5 mg g−1 at 75 °C and 1 bar) than other mesoporous silica-supported amine sorbents, and provided a durable adsorption performance.