Nanoconfined Ultrathin Polymer Membrane for Ultrafast Separation of Biobutanol from Water

Abstract Efficient recovery of biobutanol, a next‐generation biofuel, from fermentation liquor remains challenging due to its low concentration and volatility. This study introduces ultrathin rubbery polymer membranes developed through an interfacial dissolution–crosslinking method, with cross‐linked polysiloxane confined within the permanent nanovoids of ceramic alumina substrates. The resulting membranes, which are less than 10 nm thick, achieve unparalleled performance: concentrating 1.0 wt% aqueous n ‐butanol 14.2‐fold with a record‐high liquid flux of 110 kg m −2 h −1 —one to two orders of magnitude greater than those of previously reported membranes. These advancements suggest significant reductions in the membrane area and operational costs for large‐scale biobutanol separation, establishing a sustainable and economical solution for biofuel production.