Industrial-scale thermal separation processes have contributed greatly to the rise in carbon dioxide emissions. Porous materials, such as metal-organic frameworks (MOFs), can potentially reduce these emissions by achieving nonthermal chemical separations through the physical adsorption of targeted species with high selectivity. Here, we report the synthesis of the channel-based MOFs NU-2000 and NU-2001, which are constructed from three-dimensional (3D) linkers, to separate the industrially relevant xylene isomers under ambient conditions by leveraging sub-Ångstrom differences in the sizes of each isomer. While the rotation of two-dimensional (2D) linkers in MOFs often affords changes in pore apertures and pore sizes that are substantial enough to hinder separation efficiency, increasing the linker dimensionality from 2D to three-dimensional (3D) enables precise control of the MOF pore size and aperture regardless of the linker orientation, establishing this design principle as a broadly applicable strategy.
Keywords: flexibility; metal−organic frameworks; separation; xylenes.