In this study, we report the discovery of novel molecular engineering and membrane fabrication that can synergistically produce polymeric membranes exhibiting separation performance approaching ceramic membranes in biofuel dehydration. Biofuel has emerged as one of the most strategically important sustainable fuel sources. The success of biofuel development is not only dependent on the advances in genetic transformation of biomass into biofuel, but also on the breakthroughs in separation of biofuel from biomass. The “separation” alone currently accounts for 60 to 80% of the biofuel production cost. There mainly exist two kinds of materials applied for biofuel separation by pervaporation, namely, ceramic membranes and polymer membranes. Ceramic membranes made of sophisticated processes have shown separation performance far superior to polymeric membranes. Nevertheless, ceramic membranes seriously suffers fragility and high fabrication cost, and polymeric membrane with excellent flexibility is still attractive. For the polymeric membrane, extensive studies exist on how to “finetune” the membrane's pore structure including it's cross-sectioin morphology by the selection of polymer solvents and non-solvents, additives, residence times and other parameters during non-solvent induced phase separation. The key for the performance is the very thin “skin” layer which enables a high permeability. The newly discovered membranes in current work are fabricated by dual-layer co-extrusion technology in just one step through phase inversion. The best performance obtained was a total flux of ~3.9 kg/m2-hr with a separation factor of ~800 in tert-butanol dehydration. The combined molecular engineering and membrane fabrication approach may revolutionize future membrane research and development for purification and separation in energy, environment, and pharmaceuticals.