Modulation of the Pore Environment in Pillar-Layered MOFs for One-Step Purification of Ethylene

Abstract

Due to the extremely similar physical and chemical properties of C₂H₆, C₂H₄, and C₂H₂, purifying ethylene from the C₂ ternary mixture in one-step is very challenging. In this work, we developed a series of pillar-layered MOF materials ((Ni(BTC)(Bipy), Ni(BTC)(3-Me-Bipy), and Ni(BTC)(3-NH₂-Bipy)) through the functionalization of pillar ligands using pore engineering strategies. Single-component adsorption isotherm measurements demonstrate that these materials preferentially adsorb C₂H₆ and C₂H₂, thereby achieving one-step purification of the three C₂ hydrocarbons to obtain C₂H₄. By introducing functional groups on the pillars, the selectivity for C₂H₆/C₂H₄ increased by over 10%, while the selectivity for C₂H₂/C₂H₄ increased by more than 300%. Specifically, Ni(BTC)(3-NH₂-Bipy) exhibits a selectivity of 1.5 for C₂H₆/C₂H₄ (50/50, V/V) and 5.16 for C₂H₂/C₂H₄ (1/99, V/V). Under ambient conditions, the adsorption capacity of Ni(BTC)(3-NH₂-Bipy) for C₂H₂ reached 121.6 cm³/g, Ni(BTC)(3-NH₂-Bipy) exhibits superior C₂H₂ adsorption capacity and C₂H₂/C₂H₄ selectivity compared to many classic materials, including TJT-100, Azole-Th-1, and MOF-808-Bzz, commonly used for C₂H₄ purification from C₂ ternary mixtures. Dynamic breakthrough experiments indicate that in a ternary C₂ mixture, Ni(BTC)(3-NH₂-Bipy) preferentially captures C₂H₆ and C₂H₂, enabling one-step purification of C₂H₄.