Tuning Gate-Opening of a Flexible Metal–Organic Framework for Ternary Gas Sieving Separation

In comparison with the fast development of binary mixture separations, ternary mixture separations are significantly more difficult and have rarely been realized by a single material. Herein, a new strategy of tuning the gate-opening pressure of flexible MOFs is developed to tackle such a challenge. As demonstrated by a flexible framework NTU-65, the gate-opening pressure of ethylene (C₂H₄), acetylene (C₂H₂), and carbon dioxide (CO₂) can be regulated by temperature. Therefore, efficient sieving separation of this ternary mixture was realized. Under optimized temperature, NTU-65 adsorbed a large amount of C₂H₂ and CO₂ through gate-opening and only negligible amount of C₂H₄. Breakthrough experiments demonstrated that this material can simultaneously capture C₂H₂ and CO₂, yielding polymer-grade (>99.99 %) C₂H₄ from single breakthrough separation.