Highly permselective membranes with superior permeability and broad applicability are essential for organic solvent nanofiltration (OSN). However, conventional polyamide membranes often suffer from limited permeability, especially for non-polar solvents. We herein propose a simple yet effective strategy to fabricate polyamide membranes capable of ultrafast separation for both polar and non-polar solvents. By utilizing a non-planar amine monomer with diphenyl ether moiety, interfacial polymerization is rationally conducted at the deep eutectic solvent/alkane interface, yielding an ultrathin polyamide layer (~12 nm) with enhanced microporosity, uniform nanopores and a Janus-like microstructure. The resultant membrane demonstrates high permeability (36.6 L m⁻² h⁻¹ bar⁻¹ for methanol, 56.6 L m⁻² h⁻¹ bar⁻¹ for hexane), precise molecular sieving capability and excellent structural stability. The work provides a paradigm for developing high-performance OSN membranes through the molecular-level design and powerful control of the manufacturing process.
Conjugated microporous polymers (CMPs) are a novel class of microporous materials highly regarded as exceptional building blocks for the fabrication of high-performance organic solvent nanofiltration membranes. However, preparing CMP thin films remains a challenge, primarily due to the formation of insoluble powders via traditional solvothermal synthesis. Here, we introduce the innovative oxidative molecular layer deposition (oMLD) method for the fabrication of robust CMP membranes utilizing 3,3′-bithiophene (33DT) monomers. The oMLD method enables the direct fabrication of CMP thin films on substrates of varying shapes and allows precise control over membrane structure and separation performance by simply altering the deposition cycles. Benefiting from the abundant micropores and highly cross-linked structure, the resulting CMP membranes facilitate rapid solvent transport and present size-dependent solute–solute separations. In applications involving high-value separations, the P33DT membrane proves effective for pharmaceutical separation in organic solvents. To the best of our knowledge, this work represents the pioneering instance of fabricating CMP membranes via oMLD, significantly broadening the available preparation methods and potential separation applications for CMP membranes.
The simultaneous optimization of permeability and selectivity remains a cardinal challenge in advancing organic solvent nanofiltration (OSN). However, conventional OSN membranes are fundamentally constrained by the “trade-off” problem between permeability and selectivity. To break this limitation, we successfully prepared polyamide thin-film composite (PA-TFC) OSN membranes with both high permeability and high selectivity by incorporating cucurbit[6]uril (CB[6]) into the PA layer. The water insolubility of CB[6] was addressed through complexation with polyethyleneimine (PEI). The successful complexation of CB[6] was verified using techniques such as Ultraviolet-visible spectrophotometer (UV–Vis), Field emission scanning electron microscope (FE-SEM), and other testing approaches. The impact of CB[6] on the chemical composition and surface morphology of the PA layer was also systematically analyzed. In addition, we investigated the effects of monomer concentration on the membrane of permeability-selectivity performance. Experimental results show that the modified membrane, by building the solvent transport channels, showed significantly enhanced methanol permeability (increased by 164 %, 3.19 vs 1.21 L·m -2 ·h -1 ·bar -1 ), while preserving the satisfactory rejection capacity for small molecules (390 Da) (>90 %). Based on the physical parameters of different solvents, we further analyzed the solvent transport mechanism of the prepared OSN membrane. This study provides new insights and approaches for the design of high performance nanofiltration membranes with the aid of macrocycles.
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