Immobilization of Lewis Basic Sites into a Stable Ethane-Selective MOF Enabling One-Step Separation of Ethylene from a Ternary Mixture.

Purification of C 2 H 4 from a ternary C 2 H 2 /C 2 H 6 /C 2 H 4 mixture by one-step adsorption separation is of prime importance but challenging in the petrochemical industry; however, effective strategies to design high-performance adsorbents are lacking. We herein report for the first time the incorporation of Lewis basic sites into a C 2 H 6 -selective MOF, enabling efficient one-step production of polymer-grade C 2 H 4 from ternary mixtures. Introduction of amino groups into highly stable C 2 H 6 -selective UiO-67 can not only partition large pores into smaller cagelike pockets to provide suitable pore confinement but also offer additional binding sites to simultaneously enhance C 2 H 2 and C 2 H 6 adsorption capacities over C 2 H 4 . The amino-functionalized UiO-67-(NH 2 ) 2 thus exhibits exceptionally high C 2 H 2 and C 2 H 6 uptakes as well as benchmark C 2 H 2 /C 2 H 4 and C 2 H 6 /C 2 H 4 selectivities, surpassing all of the C 2 H 2 /C 2 H 6 -selective materials reported so far. Theoretical calculations combined with in situ infrared spectroscopy indicate that the synergetic effect of suitable pore confinement and functional surfaces decorated with amino groups provides overall stronger multipoint van der Waals interactions with C 2 H 2 and C 2 H 6 over C 2 H 4 . The exceptional performance of UiO-67-(NH 2 ) 2 was evidenced by breakthrough experiments for C 2 H 2 /C 2 H 6 /C 2 H 4 mixtures under dry and wet conditions, providing a remarkable C 2 H 4 productivity of 0.55 mmol g -1 at ambient conditions.