Simultaneous Trapping of C2 H2 and C2 H6 from a Ternary Mixture of C2 H2 /C2 H4 /C2 H6 in a Robust Metal-Organic Framework for the Purification of C2 H4

Abstract

The removal of C₂ H₂ and C₂ H₆ from C₂ H₄ streams is of great significance for feedstock purification to produce polyethylene and other commodity chemicals but the simultaneous adsorption of C₂ H₆ and C₂ H₂ over C₂ H₄ from a ternary mixture has never been realized. Herein, a robust metal-organic framework, TJT-100, was designed and synthesized, which demonstrates remarkably selective adsorption of C₂ H₂ and C₂ H₆ over C₂ H₄ . Breakthrough experiments show that TJT-100 can be used as an adsorbent for high-performance purification of C₂ H₄ from a ternary mixture of C₂ H₂ /C₂ H₄ /C₂ H₆ (0.5:99:0.5) to afford a C₂ H₄ purity greater than 99.997 %, beyond that required for ethylene polymerization. Computational studies reveal that the uncoordinated carboxylate oxygen atoms and coordinated water molecules pointing towards the pore can trap C₂ H₂ and C₂ H₆ through the formation of multiple C-H⋅⋅⋅O electrostatic interactions, while the corresponding C₂ H₄ -framework interaction is unfavorable.

Keywords: electrostatic interactions; gas separation; light hydrocarbons; metal-organic frameworks; selective adsorption.