Discrimination of p-xylene from xylene isomers by precisely tuning the spacing of an interpenetrated metal–organic framework†

Abstract

The purification of paraxylene (PX) from its isomers is a challenging task due to the similar melting points and kinetic radii of C₈ aromatics. Here, one new approach of PX separation has been studied, utilizing the adjustability of the alkyl C number on the imidazole ligand to achieve precise adjustment of the pore size of an interpenetrated metal organic framework material (SYUCT-111). Imidazole groups of SYUCT-111 act as adsorption sites to generate weak interactions with isomers, which enable SYUCT-111 to separate PX from binary, ternary, and quaternary mixed C₈ isomers. The selectivity order of SYUCT-111 for C₈ aromatic hydrocarbons is PX > EB > MX > OX. The PX/OX, PX/OX-MX and PX/OX-MX-EB selectivity values are significant at 15.13, 6.92 and 2.49, respectively. Grand Canonical Monte Carlo (GCMC) simulations revealed the reason for the high selectivity of SYUCT-111 for PX. This study provides a new approach for designing and synthesizing porous materials with separation performance for C₈ isomers.