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

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 cm(3) 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.