Enhancement of Propadiene/Propylene Separation Performance of Metal–Organic Frameworks by an Amine-Functionalized Strategy

Abstract

Here, a hexanuclear Co₆(μ₃-OH)₆ cluster-based metal-organic framework (MOF), [Co₆(μ₃-OH)₆(BTB)₂(bpy)₃]_n (JXNU-15) (bpy = 4,4'-bipyridine), with the 1,3,5-tri(4-carboxyphenyl)benzene (BTB^3-) ligand was synthesized for the challenging propadiene/propylene separation. The combination of a large pore volume and a suitable pore environment boosts the significantly high propadiene (C₃H₄) uptake (311 cm³ g^-1 at 298 K and 100 kPa) for JXNU-15. An amine-functionalized MOF of JXNU-15(NH₂) was further obtained with the 1,3,5-tri(4-carboxyphenyl)benzene analogue of 3,3″-diamino-5'-(3-amino-4-carboxyphenyl)-[1,1':3',1″-terphenyl]-4,4″-dicarboxylic ligand. The comparative studies of propadiene/propylene(C₃H₄/C₃H₆) separation performance between isostructural JXNU-15 and JXNU-15(NH₂) are provided. JXNU-15(NH₂) exhibits an impressive C₃H₄ capacity at low pressures with 69.1 cm³ g^-1 at 10 kPa, which is twice that of JXNU-15 under the same conditions. Moreover, the separation selectivity of JXNU-15(NH₂) is 1.3-fold higher as compared to JXNU-15. JXNU-15(NH₂) with enhanced C₃H₄/C₃H₆ separation performance was elegantly illustrated by gas separation experiments and theoretical simulations. This work presents an amine-functionalized strategy for the enhancement of the C₃H₄/C₃H₆ separation performance of MOF.