Electrosprayed COF-300/PDMS hybrid membranes with hierarchical microstructure for efficient bio-ethanol recovery

Pervaporation technology has shown great potential for organic solvent recovery and separations in biorefinery industry. However, industrial application of polymeric pervaporation membranes is still constrained by the slow mass transfer property and severe permeability-selectivity trade-off effect. Herein, we propose a novel electrospraying strategy to prepare high-performance covalent organic frameworks/polydimethylsiloxane (COF/PDMS) hybrid membranes with unique hierarchical microstructure for efficient bio-alcohol recovery. Organophilic COF-300 was synthesized and applied as porous fillers. COF-300/PDMS solutions were then electrosprayed on PDMS/ polyvinylidene fluoride (PVDF) substrate membranes to create hierarchical selective layer and form the electrosprayed COF-300/PDMS hybrid membranes. Correlation between electrospraying voltage, COF-300 loading, membrane morphology and ethanol/water separation performance was systematically investigated. Results indicated that COF-300 endowed membranes with higher surface roughness and improved ethanol adsorption/dissolution property (ethanol swelling degree over 40 %). The surface-electrospray method contributes to better dispersion and less sedimentation of COF-300 in the electrosprayed COF-300/PDMS hybrid membranes, which achieved high flux over 2150 g·m⁻²·h⁻¹ (2.2 times that of pure PDMS membranes) and separation factor of 8.87 in the pervaporation of 6 wt% ethanol/water solution at 50℃. The electrosprayed COF-300/PDMS (2 w% loading) hybrid membranes also presented superior long-term stability over 3 months. In view of this, we prepared a high-permeable surface-electrospayed COF-300/PDMS hybrid membrane and provide a facile strategy in fabricating COF-based pervaporation membranes for high-efficient bio-alcohol separation.