A molecular cage consisting of two free-base porphyrins connected by four flexible linkers was metalated with Co(III) to afford in good yield a bimetallic catalyst. The catalytic activity of the bis-Co(III) porphyrin molecular cage (CoCl) 2-1 was studied for the formation of cyclic carbonates from CO 2 and propylene oxide (PO) or styrene oxide (SO) with pyridine as cocatalyst. Various reaction parameters such as the molar ratio of the catalyst and the co-catalyst, the time of reaction, the temperature and CO 2 pressure were investigated. The molecular cage was shown to be a catalyst of high selectivity for the studied reactions and much more efficient to convert the epoxides to the corresponding cyclic carbonates than the monomeric Co(III) Cl meso-tetraphenylporphyrin (CoCl-TPP) model. When quantitative conversion of PO into propylene carbonate (PC) was reached (0.1 mol% catalyst, 1.2 mol% pyridine, 120°C, 30 bar of CO 2) only 23 % of PC was obtained with CoCl-TPP (0.2 mol%). This enhanced catalytic activity is attributed to the synergistic effect of the two metal sites incorporated in the framework of the molecular cage.