A tetranuclear-cluster-based MOF with a low-polarity pore environment for efficient C2H6/C2H4 separation

Abstract

Removing trace ethane (C₂H₆) from ethylene (C₂H₄) to obtain high-purity C₂H₄ is of great industrial significance. However, the construction of C₂H₆-selective metal–organic frameworks (MOFs) remains challenging, mainly because C₂H₄ has a small dynamic diameter and a large quadrupole moment. It has been reported that ultramicroporous MOFs with tailored pore sizes and a weakly polar pore environment can effectively purify C₂H₄ from C₂H₆–C₂H₄ mixtures. For this purpose, we successfully designed and synthesized one novel MOF material ZJNU-400 with a non-polar pore environment. The channel size of ZJNU-400 is equivalent to the size of the C₂H₆ molecule, which can provide a more accessible channel surface for C₂H₆. The pore environment of ZJNU-400 is rich in low-polarity aromatic groups, and uncoordinated N and O atoms can interact strongly with C₂H₆ molecules. Therefore, ZJNU-400 exhibits significant C₂H₆/C₂H₄ (50/50) selectivity (2.82) and C₂H₆ uptake (64.3 cm³ g⁻¹) at 298 K and 1 bar, which are superior to many C₂H₆-selective adsorbents. A breakthrough experiment shows that ZJNU-400 can purify C₂H₄ from a C₂H₆/C₂H₄ mixture in one step. GCMC and DFT calculations further revealed that the multiple synergistic interactions between the MOF and C₂H₆ enable efficient separation of the C₂H₆–C₂H₄ mixture. These results indicate that ZJNU-400 is a promising adsorbent for C₂H₆/C₂H₄ separation.