Guest-Induced Phase Switching in a Square Lattice Coordination Network to Enable Selective Adsorption of p‑Xylene

Flexible coordination networks (CNs) offer the potential for exceptional selectivity to enable hydrocarbon separations. The key to performance in such sorbents is guest-induced structural transformations that result in induced-fit binding. Unfortunately, the underlying mechanisms of such transformations remain largely unexplored. Herein, we report an investigation of the phase switching behavior of the square lattice (sql) CN [Cu­(4,4′-bipyridine)2(CF3CO2)2]n (sql-1-Cu-CF3CO2) induced by xylene adsorption. Competitive adsorption studies in binary and ternary xylene mixtures revealed high p-xylene (PX) selectivity of 10.83 over o-xylene (OX) and of 14.18 over m-xylene (MX), with an overall PX selectivity of 10.01, surpassing most commercial sorbents such as zeolites. Crystallographic studies revealed three distinct xylene-loaded phases with varying pore/channel dimensions and porosity: 1D (void: 33.9%) for PX, 2D (void: 45.8%) for OX, and 3D (void: 48.4%) for MX. The PX-loaded structure exhibited the smallest void but the strongest host–guest interactions, making it the preferred phase for PX separation from xylene mixtures.