A high-flux organic solvent nanofiltration membrane with binaphthol-based rigid-flexible microporous structures

Abstract

Highly permeable organic solvent nanofiltration (OSN) membranes are desired to be used in an efficient and energy-saving chemical separation process. Herein, we fabricated a high-flux OSN membrane by synthesizing 7,7′-dihydroxy-2,2′-binaphthol (7,7′-OH-BINOL) as an aqueous phase monomer to react with trimesoyl chloride (TMC) via interfacial polymerization. The unique structures of 7,7′-OH-BINOL having a rotatable highly kinked unit and a rigid binaphthol ring endow the fabricated polyarylate membrane with very high microporosity and super-high Young's modulus. Both simulated and experimental results demonstrate that the BINOL-based polyarylate (PAR-BINOL) membrane has two types of micropores including cross-linked pores and stacked pores. Our results find that the PAR-BINOL membrane exhibits very high solvent permeance over a wide range of solvents with diverse polarity, and also possesses a long-term stable separation performance in solvents. Impressively, the membrane solvent permeance can reach up to 28.7 L m⁻² h⁻¹ bar⁻¹, 9.2 L m⁻² h⁻¹ bar⁻¹ and 6.7 L m⁻² h⁻¹ bar⁻¹ for acetone, methanol, and dimethylformamide (DMF), respectively. The rejection of tetracycline (TC, M_w = 444 g mol⁻¹) is 98.2%. Our work provides some insights into the molecular engineering of monomers with unique contorted and rigid structures for the fabrication of highly permeable OSN membranes.