Reverse shape selectivity of hexane isomer in ligand inserted MOF-74

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

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 π* back-bonding between the transition metal and dinitrogen molecule while weakening the σ 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.

Nanoconfinement and mass transport in metal-organic frameworks

The ubiquity of metal-organic frameworks in recent scientific literature underscores their highly versatile nature. MOFs have been developed for use in a wide array of applications, including: sensors, catalysis, separations, drug delivery, and electrochemical processes. Often overlooked in the discussion of MOF-based materials is the mass transport of guest molecules within the pores and channels. Given the wide distribution of pore sizes, linker functionalization, and crystal sizes, molecular diffusion within MOFs can be highly dependent on the MOF-guest system. In this review, we discuss the major factors that govern the mass transport of molecules through MOFs at both the intracrystalline and intercrystalline scale; provide an overview of the experimental and computational methods used to measure guest diffusivity within MOFs; and highlight the relevance of mass transfer in the applications of MOFs in electrochemical systems, separations, and heterogeneous catalysis.