Designing pore size and pore electronegativity environment in aluminum-based MOF membranes for efficient cyclohexanone/cyclohexanol separation

Metal-organic framework (MOF) membranes have shown great promise for pervaporation separation due to the merit of the low carbon footprint relative to the traditional distillation process. The poor selectivity of the membrane in the cyclohexanone/cyclohexanol pervaporation separation process is one of the key factors limiting the application of the MOF membrane. Herein, pore size and electronegativity in the pore environment of MOF membranes were rationally designed for discriminating cyclohexanone and cyclohexanol molecules. Compared to the aluminum-based MOF Membranes including the CAU-23 and KMF-1 membranes, the MIL-160 membrane had a shorter-length ligand to get a smaller pore size for efficient cyclohexanone/cyclohexanol molecular sieving. Meanwhile, the stronger interaction between a highly electronegative O in the furan ring of the ligand in the MIL-160 membrane and the cyclohexanone molecule relative to the cyclohexanol led to the high adsorption difference of cyclohexanone and cyclohexanol. The MIL-160 membrane exhibited a total flux of 120 g m⁻² h⁻¹ and the highest cyclohexanone/cyclohexanol separation factor of 36, 10.2-fold and 3.8-fold separation factor compared with the CAU-23 and KMF-1 membranes and 72-fold and 2-fold separation factor compared with the reported ZIF-78 and Cu₂O@g–C₃N₄–PVDF membranes, respectively. This research demonstrates that simultaneously designing pore size and electronegativity in the pore environment is a promising way to enhance the pervaporation performance of MOF membranes.