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 (C₂ H₄ ), acetylene (C₂ H₂ ), 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 C₂ H₂ and CO₂ through gate-opening and only negligible amount of C₂ H₄ . Breakthrough experiments demonstrated that this material can simultaneously capture C₂ H₂ and CO₂ , yielding polymer-grade (>99.99 %) C₂ H₄ from single breakthrough separation.