High storage capacity and separation selectivity for C2 hydrocarbons over methane in the metal–organic framework Cu–TDPAT

Abstract

We report an rht-type metal–organic framework (MOF) which exhibits a high adsorption capacity for C ₂ hydrocarbons and excellent selectivity over CH ₄. This MOF displays the highest reported C ₂H ₂–CH ₄ selectivity of 127.1 as well as a record high value for C ₂H ₄ adsorption enthalpy (49.5 kJ mol ⁻¹).

Abstract

We report on the storage capacity and separation selectivity of an rht-type metal–organic framework, Cu–TDPAT [TDPAT = 2,4,6-tris(3,5-dicarboxylphenylamino)-1,3,5-triazine], for C ₂ hydrocarbons over CH ₄. Henry's constant, the isosteric heat of adsorption and the ideal adsorbed solution theory selectivity were calculated based on single-component sorption isotherms. Theoretical calculations indicate that both the open metal sites and the Lewis basic sites have strong interactions with the C ₂ molecules. The combination of these two kinds of sites lead to the highest C ₂H ₂–CH ₄ selectivity of 127.1 as well as record high values for C ₂H ₄ adsorption enthalpies. To mimic real-world conditions, breakthrough experiments were conducted on an equimolar four-component mixture containing C ₂H ₂, C ₂H ₄, C ₂H ₆ and CH ₄ at room temperature and 1 atm pressure. Our results show that Cu–TDPAT is a promising candidate for CH ₄ capture and purification.