Theoretical study of induced selective N2 binding under an electric field in MOF-74: application for N2/CH4 separations

Abstract

In this theoretical study, selective binding of dinitrogen to the coordinatively unsaturated metal site in M-MOF-74 (M = Mg, Mn, Fe, Co, Ni, Cu, Zn) under an external electric field is investigated. Simulation results suggest that an external electric field enhances the pi* back-bonding between the transition metal and dinitrogen molecule while weakening the sigma bond between the metal and other small gas molecules such as CO2 and CH4. In particular, Co-MOF-74 and Fe-MOF-74 show the highest dinitrogen binding energy in the presence of an electric field, twice as high as that of methane. Our work demonstrates that the asymmetric effect of the electric field on different gas molecules can serve as another dimension of design that can be exploited in small gas molecule separation in metal-organic frameworks.