Efficient isolation of C4 olefins is of paramount importance in petrochemical industry yet a challenging task owing to their similar physical properties. Sulfonate anion-pillared hybrid ultramicroporous materials (HUMs), namely TMOF-1 and ZU-619 were reported for the efficient separation of ternary C4 olefin mixtures (C4H6/n-C4H8/iso-C4H8). The geometry of adsorption sites was controlled via tuning the interpenetration direction of sulfonate anions through varying the length of anions. Interestingly, ethanedisulfonate anions in TMOF-1 exhibit the vertically interpenetrated direction, leading to TMOF-1 with pore size of 4.5 Å to excludes iso-C4H8. Furthermore, the vertical interpenetration makes the adjacent anions behave as synergetic adsorption sites for n-C4H8 and C4H6 trapping, thus endowing TMOF-1 with strong host-guest interactions and the benchmark Henry coefficient separation selectivities for C4H6/iso-C4H8 (519.2) and n-C4H8/iso-C4H8 (93.2) mixtures. In contrast, ZU-619 with butanedisulfonate anions as pillars exhibits normal interpenetration framework, giving rise to the anion-restricted pore size of 9.4 Å. The separation efficiency was confirmed by breakthrough experiments, the results presented that TMOF-1 showed excellent separation performances for C4H6/n-C4H8/iso-C4H8 mixtures and ZU-619 can be a good candidate for C4H6/n-C4H8 separation.

Geometry control of adsorption sites in sulfonate-pillared hybrid ultramicroporous materials for efficient C4 olefin separations

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