Mimicking nature seems to be one of the smartest strategies to design novel catalysts for CO₂ conversion under mild conditions. Herein, we report a facile and efficient method to construct two amide-functionalized heterometallic helicate cages as “enzyme mimic” catalysts for the synthesis of cyclic carbonates. These helicate cages show high thermal stability and exceptionally high catalytic activity and size-dependent selectivity toward small epoxides in catalytic CO₂ cycloaddition to obtain cyclic carbonates even under ambient conditions. The construction of this novel functionalized cage provides an efficient approach for realizing CO₂ conversion under mild conditions.