The objective of the present study is to develop a new type of "molecular basket" sorbent (MBS) by using inexpensive and commercially available carbon materials instead of mesoporous silica molecular sieves as supports for CO2 capture from flue gas. Several commercial carbon materials, including activated carbons and carbon blacks, with different pore sizes and pore volumes have been used to prepare the carbon-based MBS (CB-MBS) by loading the CO2-philic polyethylenimine (PEI) on them. The CO2 sorption performance of the prepared CB-MBS was evaluated by using a thermogravimetric analyzer and a fixed-bed flow sorption system. Effects of the pore properties of the carbon supports, PEI loading amount, sorption temperature, and moisture on the sorption capacity were examined. A sorption capacity of 135 mg-CO2/g-sorb was obtained by loading 50 wt % PEI on a carbon black, which is almost the same as that of PEI(50)/SBA-15 prepared by loading 50 wt % PEI on SBA-15. The higher CO2 sorption capacity of 154 mg-CO2/g-sorb was achieved when increasing the PEI loading on the carbon black to 65 wt %. Characterization of the porous structure of the carbon materials indicates that the high sorption capacity of the carbon-black-supported PEI sorbents can be ascribed to their high pore volume and large pore size. It was further found that the volume-based capacity of PEI(50)/C4 was even higher than that of PEI(50)/SBA-15 by 57% due to the higher packing density (0.35 g/mL) of the former than that (0.22 g/mL) of the latter. Because of its high CO2 sorption performance and low preparation cost, the carbon-based MBS could be a promising sorbent for cost-efficient CO2 capture from flue gas.