In situ fabrication of MOF nanoparticles in PDMS membrane via interfacial synthesis for enhanced ethanol permselective pervaporation

Biofuels separation using membranes becomes one of the research focuses in the field of renewable energy. In this study, a series of mixed matrix membranes (MMMs) with defect-free active layer around 1 µm thickness were elaborately prepared through interfacial synthesis for ethanol permselective pervaporation. Polydimethylsiloxane (PDMS) was employed as polymer matrix, which adjusted the nucleation of MOF precursors to in situ generate ZIF-8 nanoparticles. Within the active layer, the resultant ZIF-8 nanoparticles provided the preferential pathways for ethanol due to their ultrahigh adsorption capacity and super-hydrophobicity. Moderate aggregation could form the relatively continuous diffusion pathways. This approach rendered the uniform dispersion of ZIF-8 nanoparticles within PDMS matrix and their excellent compatibility. The ZIF-8 nanoparticles endowed the membranes with enhanced ethanol affinity, hydrophobic property, and thermal stability. More importantly, the ZIF-8 nanoparticles substantially reduced the permeation energy barriers of the membrane for penetrants. The membranes displayed the simultaneous increase in permeation flux and separation factor when utilized for ethanol recovery from aqueous solution, revealing the desirable anti-tradeoff effect. Particularly, the resultant membrane exhibited a superior pervaporation performance with relatively high permeation flux (1778 g·m^-2·h^-1) and comparable separation factor (12.1) in separating 5.0 wt% ethanol aqueous solution at 40 °C.