Fluoride-assisted ultradilute precursor synthesis of defect-free thin FAU zeolite membrane for pervaporation dehydration

Pervaporation (PV) is a promising alternative to distillation for biofuel dehydration, yet fabricating thin, defect-free zeolite membranes remains challenging. In this work, a synergistic strategy combining nanoseeds, fluoride mineralizers, and ultradilute precursors was developed to construct high-quality faujasite (FAU) membranes. Nanoseeds provided compact seed layers, fluoride promoted crystal intergrowth while suppressing non-selective channels, and ultradilute precursors slowed crystallization yielding ~2.4 μm membranes with low defect density. Performance analysis confirmed that PV separation followed an adsorption-diffusion mechanism. The optimized membrane achieved excellent fluxes of 3.70 kg/(m 2 h) with a separation factor of 1520 for a 10 wt% water/isopropanol mixture and 6.01 kg/(m 2 h) with a separation factor of 742 for a 20 wt% water/ n -butanol mixture. These results surpassed the results of previously reported membranes and demonstrated how this cooperative strategy provides a viable pathway for scalable fabrication of defect-free thin zeolite membranes.