Porous liquid ZIF-67-integrated PDMS mixed matrix membranes for efficient bioethanol dehydration

Energy efficient dehydration of fermentation broths is a critical bottleneck in bioethanol production, where conventional distillation imposes a high thermal and carbon penalty. Pervaporation using polymer–inorganic hybrid membranes offers a promising low-energy alternative, provided that membrane exhibits both high flux and selectivity to alcohols. Here, we demonstrate that incorporating a porous liquid (PL) form of ZIF-67 into polydimethylsiloxane (PDMS) mixed matrix membranes (MMMs) enables simultaneously high flux and selectivity for ethanol dehydration via pervaporation. ZIF-67 crystals were first synthesized and then converted into a Type-3 porous liquid through N-heterocyclic carbene functionalization and dispersion in mesitylene, yielding a flowable, solution-processable MOF phase. This PL was incorporated into PDMS at loadings up to 40 wt% without aggregation or interfacial defects, overcoming the dispersion and compatibility limitations typically observed with solid MOF fillers. Pervaporation tests using a 6 wt% ethanol/water feed showed that the 40 wt% ZIF-67-PL membrane achieved a total flux of 3.5 kg·m⁻²·h⁻¹ and a separation factor of 19.8 at 65 °C, corresponding to approximately a 170 % increase in flux and a 205 % enhancement in separation factor compared to pristine PDMS. Benchmarking against state-of-the-art PDMS-based MMMs highlights ZIF-67-PL/PDMS membranes as a high-performance, scalable platform for bioethanol dehydration and, more broadly, for next-generation porous-liquid-enabled separations.