Highly selective, high capacity separation of o‐xylene from C8 aromatics by a switching adsorbent layered material

Adsorbent materials that exhibit high selectivity without sacrificing adsorption capacity can significantly reduce energy costs for industrial separation/purification processes and thus facilitate a transition away from energy‐intensive processes such as conventional distillation. Purification of the C8 aromatics (xylenes and ethylbenzene) is particularly challenging because of their similar physical properties. It is also relevant because of their industrial utility. In this context, physisorptive separation of C8 aromatics has long been suggested as an energy efficient solution but no physisorbent has yet combined high selectivity (>5) with high adsorption capacity (>50 wt%). Herein, we report a counterintuitive approach to the adsorptive separation of o‐xylene from other C8 aromatics by the study of a known nonporous layered material, [Co(bipy)2(NCS)2]n (sql‐1‐Co‐NCS). We observe that sql‐1‐Co‐NCS can reversibly switch to C8 aromatics loaded phases with different switching pressures and kinetics, manifesting benchmark o‐xylene selectivity (SOX/EB ~ 60) and high saturation capacity (> 80 wt%). Structural insight into the observed selectivity and capacity is gained via analysis of the crystal structures of C8 aromatics loaded phases.

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