Cage compounds offer a unique opportunity to capture CO2, but a perfect design has been elusive. Herein, we computationally designed cage compounds by using linkers to connect two calix[4]pyrrole units together into a cage for capturing CO,. Quantum mechanical calculations based on dispersion-corrected density functional theory show that the (CH2) linker has an optimal length at n = 5 where the N-H groups from the pyrrole molecules form four H center dot center dot center dot O interactions with the two terminal 0 atoms of CO,. The cationic and zwitterionic cages can also achieve high CO, affinity and CO2/N-2 selectivity in the cage cavity compared with previously synthesized cages. Based on the computed potential energy curves of gas entering the cage, we conclude that all the cages are easily accessible by CO,. This work shows that the calix-based cages have great potential for selective CO, capture.