High performance microporous polyesteramide organic solvent nanofiltration composite membrane prepared from a twisted diamono-diphenol monomer

Organic solvent nanofiltration (OSN) is a promising, energy-efficient separation technique for molecular separations and solute enrichment in organic media. However, the facile construction of high-performance and stable OSN membranes remains a persistent challenge. Here, we report a newly developed microporous composite membrane with exceptional perm-selectivity, achieved by employing a new aqueous phase monomer, 9,9-bis(3-amino-4-hydroxyphenyl)fluorene (BAHPF), which features two amino and two phenolic reactive groups, through interfacial polymerization (IP) with trimesoyl chloride (TMC). Ultrathin polyesteramide nanofilms with thicknesses less than 20 nm were achieved. The rigid, twisted, and multifunctional characteristics of BAHPF monomer endowed the resulting polyesteramide layer with significantly improved microporosity and a highly interconnected polymeric network voids. As a result, the optimized BAHPF/TMC membrane demonstrated a methanol permeance of up to 17.9 ± 1.8 LMH/bar, while preserving a low MWCO of 298 Da, surpassing the performance of most reported polymeric OSN membranes. Furthermore, the membrane exhibited excellent long-term operational stability and achieved high retention capacities (>98 %) for three model small-molecule drugs. Notably, the heat-sensitive drug rifampicin was effectively concentrated by ∼14-fold, from 50 ppm to ∼700 ppm, within 5 h. Overall, this work offers novel insight into the material design approach for developing next-generation high-performance organic solvent nanofiltration membranes.