A highly stable metal–organic framework via pore aromatization for efficient natural gas purification with record C3H8 and C2H6 uptake

Abstract

Selective capture of C₃H₈ and C₂H₆ from CH₄ is extremely key in natural gas purification, but there is a trade-off between uptake and selectivity. Herein, we proposed a method for pore aromatization to build an ultramicroporous metal–organic framework Ni(ndc)(dabco)_0.5 with a robust structure and examine its separation performance for C₃H₈/CH₄ and C₂H₆/CH₄ mixtures. The pore walls of the material are composed of opposite and parallel naphthalene rings with a pore size of 6.0 Å and rich electronegative binding sites, and the overlapping areas between naphthalene rings form extremely strong potential energy overlaps. This MOF owns a record C₃H₈ and C₂H₆ uptake (91.4 and 46.5 cm³(STP) g⁻¹) in actual natural gas components at 298 K and 0.05 and 0.1 bar respectively with excellent C₃H₈ (119.0 cm³(STP) g⁻¹) and C₂H₆ (116.6 cm³(STP) g⁻¹) and 1.0 bar, presenting a strong binding ability toward C₃H₈ and C₂H₆. Meanwhile, the IAST-predicted C₃H₈/CH₄ (1947.4) and C₂H₆/CH₄ (42.6) selectivity is also superior to all adsorbents so far, only inferior to BSF-2, thus overcoming the aforementioned trade-off and setting a novel benchmark. The theoretical studies imply that the enhanced C₃H₈ and C₂H₆ adsorption performance is attributed to the aromatized ultramicropores modified by dense low-polarity naphthalene rings, causing a strong affinity for the two gases. Additionally, the breakthrough test proved that the C₃H₈/CH₄ and C₂H₆/CH₄ accompanied by C₃H₈/C₂H₆/CH₄ mixtures were fully separated at ambient temperature with superb recyclability. Accordingly, these results confirm the great potentiality of Ni(ndc)(dabco)_0.5 for natural gas purification.