Molecular Sieving of Acetylene from Ethylene in a Rigid Ultra-microporous Metal Organic Framework

Abstract

Rigid molecular sieving materials are the ideal candidates for gas separation (e. g., C₂ H₂ /C₂ H₄ ) due to their ultrahigh adsorption selectivity and the absence of gas co-adsorption. However, the absolute molecular sieving effect for C₂ H₂ /C₂ H₄ separation has rarely been realized because of their similar physicochemical properties. Herein, we demonstrate the absolute molecular sieving of C₂ H₂ from C₂ H₄ by a rigid ultra-microporous metal-organic framework (F-PYMO-Cu) with 1D regular channels (pore size of ca. 3.4 Å). F-PYMO-Cu exhibited moderate acetylene uptake (35.5 cm³ /cm³ ), but very low ethylene uptake (0.55 cm³ /cm³ ) at 298 K and 1 bar, yielding the second highest C₂ H₂ /C₂ H₄ uptake ratio of 63.6 up to now. One-step C₂ H₄ production from a binary mixture of C₂ H₂ /C₂ H₄ and a ternary mixture of C₂ H₂ /CO₂ /C₂ H₄ at 298 K was achieved and verified by dynamic breakthrough experiments. Coupled with excellent thermal and water stability, F-PYMO-Cu could be a promising candidate for industrial C₂ separation tasks.

Keywords: ethylene production; gas separation; molecular sieving; ultra-microporous metal organic frameworks.