Efficient separation of C4 olefins with fluorinated anion-pillared hybrid ultramicroporous materials by gate-opening and size-sieving effect

In the petrochemical industry, the separation of C4 olefins is crucial but a challenging and energy-intensive process. In this study, two fluorinated anion-pillared hybrid ultramicroporous materials (HUMs), namely KAUST-7 (NbOFFIVE-1-Ni) and KAUST-8 (AlFFIVE-1-Ni), were explored for the efficient separation of ternary C4 olefin mixtures (C 4 H 6 /n-C 4 H 8 / iso -C 4 H 8 ) via gate-opening and size-sieving effects. KAUST-7, with a narrow and flexible pore window that completely excludes iso -C 4 H 8 , but allows for the absorption of C 4 H 6 and n-C 4 H 8 through gate-opening effects, with a preferential adsorption of C 4 H 6 due to its easier access to the channel. KAUST-8, on the other hand, with a larger pore window size and the strong H-bond interactions between the electronegative fluorine atoms from inorganic anion pillar and the C4 olefin molecules, efficiently separates iso -C 4 H 8 from C4 olefins, as the adsorption of both C 4 H 6 and n-C 4 H 8 is significantly enhanced while iso -C 4 H 8 retains much lower adsorption capacity. The relationship between the structures and separation properties of these materials is discussed, providing insight into the development of efficient separation materials. Fixed bed breakthrough experiments verify the excellent separation performances of KAUST-7 and KAUST-8 for C 4 H 6 /n-C 4 H 8 / iso -C 4 H 8 , highlighting their potential for industrial applications.