Metal organic frameworks (MOFs) are one kind of promising porous materials for CO 2 capture and separation. In this work, the chelation of the first-row transition metals (from Sc to Zn) into MOFs was proposed to enhance its CO 2 adsorption capacity. The adsorption mechanisms and adsorption capacities of CO 2 in the chelated MOFs were explored by using quantum mechanical calculation and QM-based grand canonical Monte Carlo simulations. The results show that the chelation of transition metals can significantly improve the adsorption capacity of CO 2 in MOFs, especially at low pressure. Among the first row transition metals, the chelation of Mn(II), Fe(II), Co(II), Ni(II), Cu(II), and Zn(II) gives higher binding energies than other transition metals. The chelation of Mn(II) into MOFs shows the highest uptake amount at low pressure. The CO 2 uptake amounts in UiO(bpydc)-MnCl 2 and BPV-MOF-MnCl 2 are about six times higher than the original counterparts at 298 K and 100 kPa. Based on this significant enhancement, the chelation of transition metals in MOFs provides an efficient approach for enhancing CO 2 capture.