Imidazole-bearing covalent organic framework hybrid membranes toward toluene/n-heptane separation

Molecular refining such as aromatics/alkanes separation has emerged as the dominant trend in the petrochemical industry, which can maximize the value of all feedstock molecules in naphtha. Covalent organic framework (COF) possesses exceptional structural design and functionalization flexibility, enabling facile incorporation of ordered structure and functional groups that can enhance the selective diffusion of aromatic components. Here, an imidazole-bearing COF (TpDAB) was designed and incorporated into Pebax matrix to prepare hybrid membranes for toluene/ n -heptane pervaporation separation. Imidazole groups selectively enhanced aromatics affinity by inducing p-orbital electron polarization in benzene rings. The imidazole-bearing COF can effectively maintain the pore size of the COF. The nanoscale pores of COF enabled rapid mass transfer. These features synergistically improved the flux and separation factor. Especially for the hybrid membrane with TpDAB content of 0.3 wt%, the highest performance was achieved with flux of 964 g m −2  h −1 and separation factor of 7.60 for 50 wt% toluene/ n -heptane mixture. Moreover, this study preliminarily explored the preparation of hollow fiber membrane (HFM), offering a potential pathway for the practical application of COF hybrid membrane.