Adsorption-diffusion dual-driven (Zr/Ti)-UiO-66/tPIM-1 mixed-matrix membranes for efficient hexane isomer separation

The separation of hexane isomers in petrochemical engineering is energy-intensive, driving the need for membrane-based alternatives to conventional thermal processes. Mixed-matrix membranes (MMMs) offer a material platform by combining the processability of polymer matrices with the high structural tunability of porous fillers. In this work, we fabricate UiO-66-Tix/tPIM-1 MMMs by incorporating Ti-regulated bimetallic Zr/Ti-UiO-66 fillers into a thermally treated polymer of intrinsic microporosity (tPIM-1) matrix. At low Ti contents, the UiO-66-type crystallinity is largely preserved, while Ti introduction produces measurable changes in the pore characteristics and nHex/22DMB adsorption kinetics. Membrane-level sorption measurements show preferential nHex uptake, while adsorption-kinetic analysis and molecular dynamics simulations of both the isolated frameworks and the UiO-66-Ti 0.2 /tPIM-1 composite environment indicate stronger diffusion restriction toward bulky 22DMB than toward linear nHex. Collectively, these results support an adsorption–diffusion transport mechanism for the observed separation behavior. Among the Ti contents and filler loadings investigated, the selected 5 wt% UiO-66-Ti 0.2 /tPIM-1 membrane achieves a flux of 515 g·m −2 ·h −1 and a separation factor of 7.9 for nHex/22DMB separation. The membrane also maintained relatively stable performance during 84 h of continuous operation and preferentially enriched nHex from multicomponent C6 isomer mixtures, showing competitive separation performance among reported MMMs for hexane isomer separation. These results indicate that controlled Ti introduction provides a route to modify the pore characteristics of UiO-66 and improve nHex/22DMB discrimination in thermally treated PIM-1-based MMMs.