The encouraging improvement of polyamide nanofiltration membrane by cucurbituril‐based host–guest chemistry

Abstract

The considerable performance enhancement of small molecule‐sieving nanofiltration membrane has been achieved by the functional combination between host–guest chemistry and interfacial polymerization (IP) for the first time in this work. First, the water‐insolubility of cucurbit[6]uril (CB6) was ameliorated by constructing host–guest complex (CB6‐PIP) with piperazine. Second, the incorporation of water‐soluble CB6‐PIP in the selective layer via IP leads to the generation of not only the enlarged conventional polyamide network tunnels but also rotaxane tunnels. Such enrichment of solvent transport tunnels contributes to an amazing pure water permeability of 15.5–25.4 Lm−2bar−1h−1, three times higher than that of traditional polyamide membranes, with a high R/MgSO4 of 99.5–92.5%, perfect SO42−/Cl− selectivity due to the electronegative contribution of CB6, as well as untapped potential in organic solvent nanofiltration. This work not only provides a fire‐new strategy to design new type of NF materials but also promotes the application of CBs in many other fields.

Engineering membranes with macrocycles for precise molecular separations

“…In addition to CD, other macrocycle molecules have been investigated to synthesize mixed matrix and thin-film nanocomposite membranes, due to their special characteristics such as pore structure and chemical properties. 136 Using Cucurbit [6]uril (CB6)-piperazine (PIP) pseudorotaxane as the aqueous monomer, CB-containing TFN membranes were then prepared by IP (Fig. 7c).…”

“…134 (c) i) The diffusion of i) CB6-PIP in the two phase interface, ii) the sketch of the surface topography of NF-CB-1 membranes, iii) the SEM and AFM images for NF-0.1%CB-1 membrane. 136 Reproduced with permission from Royal Society of Chemistry, Copyright 2015, American Chemical Society, Copyright 2015, and Wiley-VCH, Copyright 2019.…”

“…Besides CD-based membrane, a few other macrocycle molecules have been applied to prepare membranes for OSN. 136,212 For example, Zhai et al prepared a polyarylate membrane from the waterwheel-like macrocycle Noria via interfacial polymerization. 212 The rejections of the resulting Noria membrane increased with the molecular weights of various dyes, leading to a molecular weight cut-off of 820 g/mol.…”

Breaking through permeability–selectivity trade‐off of thin‐film composite membranes assisted with crown ethers

“…2 Various water treatment technologies have been exploited in the past few decades to produce clean water. 3,4 For example, membrane-based separation techniques such as ultrafiltration, nanofiltration, [5][6][7] reverse osmosis and forward osmosis (FO) [8][9][10] have been implemented at various levels for desalination, wastewater and water treatment. The heart of the successful implementation of these technologies is a high-performance membrane with superior separation efficiency and excellent fouling resistance.…”

Alicyclic polyamide nanofilms with an asymmetric structure for Cl−/SO42−separation

“…12 In addition, efforts have been made to fine-tune the surface charge and porosity of PA nanofilms to improve the membrane performance. Specifically, surface coating, [13][14][15] an intermediate layer, 16,17 alternative amine or acid chloride monomers, 3,18,19 additives including surfactants, 12,20 macromolecules, 21,22 and nanoparticles 23,24 have been adopted to successfully achieve a high separation selectivity and high permeation performance. It has been found that a trade-off occurs between water/salt or ion selectivity and pure water permeance.…”