Guest molecule engineered pore aperture of a yttrium-based metal–organic framework for efficient 1,3-butadiene separation from C4 hydrocarbons

Molecular sieving separation of 1,3-butadiene (C4H6) from C4 hydrocarbons is a highly desired method for C4H6 purification while it is still a challenge to finely tune the pore aperture size of metal–organic framework (MOF) adsorbent. To develop molecular-sieving MOFs for gas separation, most efforts mainly focus on the precise control of intrinsic window size of MOF framework while little effort has focused on regulating the pore size of MOF by guest molecule. In this work, we report the guest molecule engineered pore aperture strategy of MOF for molecular-sieving separation of C4H6 from other C4 hydrocarbons. As a proof-of-concept experiment, the aperture pore structure of a robust yttrium-based Y-abtc (abtc = 3, 3′, 5, 5′-azobenzene-tetracarboxylate) was adjusted by the controlled decomposition of the trapped dimethylamine cations in the pores. The optimal Y-abtc-160, which was obtained by treating the as-synthesized Y-abtc sample at 160 °C, exhibits typical type I adsorption isotherm for C4H6 at 298 K while other C4 components are excluded by size exclusion effect even at 1 bar. The C4H6 uptake in Y-abtc-160 is up to 49.5 cm3 g−1 at 1 bar, which exceeds all the reported adsorbents with ideal molecular-sieving effect. The column breakthrough experiments verify the efficient separation of C4H6/n-C4H8, C4H6/iso-C4H8, C4H6/n-C4H10, and C4H6/iso-C4H10 binary mixtures. In addition, Y-abtc-160 MOF has good regeneration ability and excellent chemical stability, implying great potential for the practical separation of C4H6 from other C4 hydrocarbons.