Introduction of π-complexation into porous aromatic framework for highly selective adsorption of ethylene over ethane

Abstract

In this work, we demonstrate for the first time the introduction of π-complexation into a Porous Aromatic Framework (PAF), affording significant increase in ethylene uptake capacity, as illustrated in the context of Ag(I) ion functionalized PAF-1, PAF-1-SO₃Ag. IAST calculations using single-component-isotherm data and an equimolar ethylene/ethane ratio at 296 K reveal that PAF-1-SO₃Ag shows exceptionally high ethylene/ethane adsorption selectivity (S_ads: 27 to 125), far surpassing benchmark zeolite and any other MOF reported in literature. The formation of π-complexation between ethylene molecules and Ag(I) ions in PAF-1-SO₃Ag has been evidenced by the high isosteric heats of adsorption of C₂H₄ and also proved by in situ IR spectroscopy studies. Transient breakthrough experiments, supported by simulations, indicate the feasibility of PAF-1-SO₃Ag for producing 99.95%+ pure C₂H₄ in a Pressure Swing Adsorption operation. Our work herein thus suggests a new perspective to functionalizing PAFs and other types of advanced porous materials for highly selective adsorption of ethylene over ethane.