Preparation of MAF-6/Polydimethylsiloxane Mixed Matrix Membranes with Tunable Hierarchical Structure and Their Pervaporation Performance

Traditional mixed matrix membranes (MMMs) face a mismatch between random filler dispersion and molecular concentration gradient during pervaporation for bioethanol recovery. To address this problem, we fabricated MAF-6/PDMS (polydimethylsiloxane) MMMs with hierarchical and asymmetric filler distribution (surface-enriched and bottom-enriched) via electrospraying and solution casting. By aligning filler enrichment with the ethanol gradient, both bioethanol recovery and filler utilization efficiency were enhanced. Effects of the asymmetric distribution of MAF-6, electrospraying voltage, MAF-6 content, and membrane morphology on the pervaporation recovery of ethanol were investigated. Results revealed that surface-electrosprayed MAF-6/PDMS MMMs possessed both the highest permeation flux and selectivity due to the alignment between the permeability profile and the ethanol concentration gradient. At 50 °C and 6 wt % ethanol, the membrane achieved a flux of 1317.45 g·m–2·h–1 and a selectivity of 9.75. This approach offers a flexible method to create asymmetric filler distribution in pervaporation membranes for efficient bioethanol separation.