Flexible Microporous Framework for One-Step Acquisition of Ethylene from Ternary C₂ Hydrocarbons

One-step purification of ethylene (C₂H₄) from ternary C₂ hydrocarbon mixtures is a crucial task and an enduring challenge because of their similar molecular size and physical properties. Owing to their intriguing structural dynamics, flexible MOFs have attracted more attention for gas adsorption and separation. Herein, we report a flexible MOF FJI-W-66 that exhibits rarely seen "breathing" behaviors for C₂ hydrocarbons. Upon activation, the channels of guest-free FJI-W-66a significantly contract to a nearly closed-pore state. FJI-W-66a shows the stepwise adsorption isotherms for C₂ hydrocarbons, which suggests the occurrence of structural transformation between less open and more open phases. Breakthrough experiments provide evidence that FJI-W-66a can selectively separate C₂H₄ from C₂H₂/C₂H₄/C₂H₆ mixtures with different ratios under ambient conditions, realizing the one-step acquisition of C₂H₄ from ternary C₂ hydrocarbons.