Methanol-Regulated Interfacial Polymerization of Fluorinated Polyamide Membranes Enables Rapid Liquid Hydrocarbon...

Interfacially polymerized polyamide membranes have revolutionized industrial desalination, yet their intrinsically polar networks are poorly suited for molecular separations in nonpolar liquid hydrocarbons. Herein, classical polyamide chemistry is extended to hydrocarbon separations through the incorporation of a hydrophobic trifluoromethyl-substituted diamine. Methanol was introduced as a cosolvent to overcome the limited aqueous solubility of the fluorinated monomer while regulating interfacial polymerization. Systematic investigation revealed how methanol-mediated interfacial reaction kinetics and fluorination collectively govern polyamide network formation and membrane structure. The resulting fluorinated polyamide membrane exhibited a 12-fold increase in toluene permeance and a 51-fold enhancement in toluene/1,3,5-triisopropylbenzene (TIPB) separation factor relative to conventional polyamide membranes. The membrane maintained 96%-98% TIPB rejection while sustaining a high average toluene permeance of 0.17 L m^{- 2} h^{- 1} bar^{- 1} during 21 days of continuous operation. Beyond model solute systems, the membrane demonstrated effective molecular discrimination in application-relevant hydrocarbon mixtures, enabling the fractionation of representative Fischer-Tropsch liquids, rapid enrichment of linear α-olefins, and efficient separation of light linear/branched alkanes as well as near-boiling hydrocarbon mixtures. This work establishes fluorinated polyamide membranes as a versatile platform for nonpolar liquid hydrocarbon separations and expands the scope of the highly scalable interfacial polymerization technology beyond aqueous applications.