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A key challenge in efficient molecular separation is fabricating large‐scale, highly selective polymeric membranes with precise pore control at the molecular scale. Herein, a new contorted monomer 6,6′‐dihydroxy‐2,2′‐biphenyldiamine (DHBIPDA) is introduced as a building block to generate cross‐linked, ultra‐thin microporous nanofilms (sub‐10 nm) via interfacial polymerization, enabling rapid, and precise molecular nanofiltration. Using diacyl chloride (TPC) as the cross‐linker instead of trimesoyl chloride (TMC) significantly reduces the pore sizes within the membranes and achieves a narrower pore distribution due to a semi‐crystalline structure. The film structures are confirmed using comprehensive characterization techniques including wide‐angle X‐ray scattering (WAXS), X‐ray diffraction (XRD), positron annihilation lifetime spectroscopy (PALS), CO2 adsorption analysis, and molecular‐scale simulation. The DHBIPDA/TPC and DHBIPDA/TMC membranes achieve methanol permeance values of up to 16.4 and 15.1 LMH bar−1 coupled with molecular weight cutoffs (MWCOs) as low as 283 and 306 Da, respectively. The DHBIPDA/TPC membrane demonstrates both higher permeance and higher selectivity compared to its relatively disordered counterpart DHBIPDA/TMC, consistent with characterization data. The DHBIPDA‐derived membrane efficiently separates dye mixtures with similar molecular weights and enables effective recycling of organometallic homogeneous catalysts, suggesting its potential for industrial applications. [ABSTRACT FROM AUTHOR]

Organic solvent nanofiltration (OSN) is an emerging membrane separation technology, which urgently requires robust, easily processed, OSN membranes possessing high permeance and small solutes‐selectivity to facilitate enhanced industrial uptake. Herein, we describe the use of two 2,2′‐biphenol (BIPOL) derivatives to fabricate hyper‐crosslinked, microporous polymer nanofilms through IP. Ultra‐thin, defect‐free polyesteramide/polyester nanofilms (≈5 nm) could be obtained readily due to the relatively large molecular size and ionized nature of the BIPOL monomers retarding the rate of the IP. The enhanced microporosity arises from the hyper‐crosslinked network structure and monomer rigidity. Specifically, the amino‐BIPOL/PAN membrane exhibits extraordinary permselectivity performances with molecular weight cut‐off as low as 233 Da and MeOH permeance of ≈13 LMH/bar. Precise separation of small dye mixtures with similar M.W. based on both their charge and molecular size are achieved. [ABSTRACT FROM AUTHOR]

Organic solvent nanofiltration (OSN) is a green, environmentally friendly and sustainable separation technology. High-performance OSN membranes are expected to play a critical role in the field of chemical separation involving organic solvents. However, traditional OSN membranes suffer from the constraints on perm-selectivity. Herein, we introduced macrocyclic molecules with intrinsic angstrom-size cavity, pillar[n]arene (P[n]a, n = 5, 6), as a novel aqueous monomer to react with trimesoyl chloride (TMC) to prepare highly perm-selective thin-film composite (TFC) OSN membranes through interfacial polymerization. The prepared TFC-P[n]a membranes exhibit ultra-thin selective layer thickness of sub-10 nm and possess permanent intrinsic microporous structure, which endows the membrane with high perm-selectivity. Especially, the TFC-P[6]a membrane exhibits a high methanol permeance (8.10 L m−2 h−1 bar−1) and a low molecular weight cut-off (MWCO) of 300 g mol−1. In addition, the prepared TFC-P[n]a membranes exhibit molecule sieving function and could discriminate molecules with similar molecular weights but different shapes. Our work provides an insight of material design for the preparation of next-generation high-performance organic solvent nanofiltration membranes. [Display omitted] • The OSN membranes were prepared via IP of macrocyclic molecules pillar[n]arene with trimesoyl chloride. • The molecular cavity of pillar[n]arene and its 3D structure provide extra channels for transportation of solvent molecules. • The TFC-P[n]a nanofilms have ultra-thin thickness of sub-10 nm. • The MWCO of the TFC-P[n]a composite membranes were as low as ≤ 300 g mol−1. [ABSTRACT FROM AUTHOR]