• Refinement of pore size at sub-angstrom precision in robust metal–organic frameworks for separation of xylenes

      Li, Xiaolin; Wang, Juehua; Bai, Nannan; Zhang, Xinran; orcid: 0000-0002-0734-6173; Han, Xue; da Silva, Ivan; orcid: 0000-0002-4472-9675; Morris, Christopher G.; Xu, Shaojun; orcid: 0000-0002-8026-8714; Wilary, Damian M.; Sun, Yinyong; orcid: 0000-0002-5570-5089; et al. (Nature Publishing Group UK, 2020-08-27)
      Abstract: The demand for xylenes is projected to increase over the coming decades. The separation of xylene isomers, particularly p- and m-xylenes, is vital for the production of numerous polymers and materials. However, current state-of-the-art separation is based upon fractional crystallisation at 220 K which is highly energy intensive. Here, we report the discrimination of xylene isomers via refinement of the pore size in a series of porous metal–organic frameworks, MFM-300, at sub-angstrom precision leading to the optimal kinetic separation of all three xylene isomers at room temperature. The exceptional performance of MFM-300 for xylene separation is confirmed by dynamic ternary breakthrough experiments. In-depth structural and vibrational investigations using synchrotron X-ray diffraction and terahertz spectroscopy define the underlying host–guest interactions that give rise to the observed selectivity (p-xylene < o-xylene < m-xylene) and separation factors of 4.6–18 for p- and m-xylenes.