MOF-74 with tailored open metal sites for mixed-matrix membrane separation of benzene/cyclohexane azeotrope

Efficient separation of aromatic/aliphatic hydrocarbon mixture represents a critical and challenging task in refinery and petrochemical industries. To date, the development of aromatic-selective membranes with superior separation efficiency has attracted increasing attention. In this work, we selected M-MOF-74 with different metal centers (M = Mn, Mg, Co) to incorporate into chitosan-polyvinyl pyrrolidone (CS-PVP) blends to fabricate aromatic-selective mixed-matrix membrane (MMM) for the improvement of aromatic/aliphatic separation performance. Among them, the Mn-MOF-74/CS-PVP MMMs displayed dramatically enhanced pervaporation performance toward benzene/cyclohexane separation, owing to the strong preferential adsorption affinity between Mn-MOF-74/CS-PVP membrane and benzene molecules via π-π interactions. Under the optimal conditions, the cross-linked membrane achieved a total flux of 129 ± 2 g m −2  h −1 and a separation factor of 15.4 ± 0.1 for separating a 50 wt% benzene/cyclohexane azeotrope at 50 °C, outperforming most state-of-the-art membranes. Long-term stability tests confirmed that the MOF-74/CS-PVP membrane possesses promising practical potential for benzene/cyclohexane azeotropic separation.