One-step ethylene separation from ternary C2 hydrocarbon mixture with a robust zirconium metal–organic framework

Abstract

One-step separation of high-purity ethylene (C2H4) from C2 hydrocarbon mixture is critical but challenging because of the very similar molecular sizes and physical properties of C2H4, ethane (C2H6), and acetylene (C2H2). Herein, we report a robust zirconium metal–organic framework (MOF) Zr–TCA (H3TCA = 4,4′,4″-tricarboxytriphenylamine) with suitable pore size (0.6 nm × 0.7 nm) and pore environment for direct C2H4 purification from C2H4/C2H2/C2H6 gas-mixture. Computational studies indicate that the abundant oxygen atoms and non-polar phenyl rings created favorable pore environments for the preferential binding of C2H2 and C2H6 over C2H4. As a result, Zr–TCA exhibits not only high C2H6 (2.28 mmol·g−1) and C2H2 (2.78 mmol·g−1) adsorption capacity but also excellent C2H6/C2H4 (2.72) and C2H2/C2H4 (5.64) selectivity, surpassing most of one-step C2H4 purification MOF materials. Dynamic breakthrough experiments confirm that Zr–TCA can produce high-purity C2H4 (>99.9%) from a ternary gas mixture (1/9/90 C2H2/C2H6/C2H4) in a single step with a high C2H4 productivity of 5.61 L·kg−1.