Cubane-doped dual-ligand Zr-MOF membranes for efficient benzene/cyclohexane separation

The separation of benzene/cyclohexane (BZ/CHX) represents a critical yet challenging task in the chemical industry, as their nearly identical boiling points and kinetic diameters render conventional distillation highly energy-intensive. Pervaporation, driven by a transmembrane pressure difference, offers an energy-efficient alternative by breaking the azeotropic equilibrium of BZ/CHX mixtures. Metal–organic framework (MOF) membranes have emerged as promising candidates for such separations owing to their exceptional structural tunability. However, their application in this context remains largely unexplored. Herein, we report a dual-ligand engineering strategy to fabricate UiO-66-CDC MOF membranes, wherein a cubic alkane ligand is incorporated into a planar parent ligand to create a dual-ligand-modified framework. This approach enables precise regulation of the pore microenvironment and enhances preferential adsorption and recognition of aromatic benzene over aliphatic cyclohexane through multiple interactions (C···C, H···C, C–H···π, C–H···O, and π···π). Consequently, under a single-stage operation with an equimolar (50:50) BZ/CHX feed, the optimized membrane delivered a permeation flux of 478 g m −2 h −1 and a separation factor of 5.8, corresponding to a 40% increase in flux and an 81% increase in separation factor, respectively, over the control membrane, and yielding a 110% higher PSI. When further applied to a two-stage membrane separation process, the total flux and separation factor reached 1747 g m −2 h −1 and 40.7, respectively, demonstrating the potential of process intensification. This dual-ligand design offers fundamental guidance for the development of advanced separation membranes targeting diverse aromatic/alkane mixtures.