Highly Selective, High‐Capacity Separation of o‐Xylene from C₈ Aromatics by a Switching Adsorbent Layered Material

Purification of the C 8 aromatics (xylenes and ethylbenzene) is particularly challenging because of their similar physical properties. It is also relevant because of their industrial utility. Physisorptive separation of C 8 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 %). Now a counterintuitive approach to the adsorptive separation of o ‐xylene from other C 8 aromatics involves the study of a known nonporous layered material, [Co(bipy) 2 (NCS) 2 ] n ( sql‐1‐Co‐NCS ), which can reversibly switch to C 8 aromatics loaded phases with different switching pressures and kinetics, manifesting benchmark o ‐xylene selectivity (S OX/EB ≈60) and high saturation capacity (>80 wt %). Structural insight into the observed selectivity and capacity is gained by analysis of the crystal structures of C 8 aromatics loaded phases.