Achieving high permeability and enhanced selectivity for Angstrom-scale separations using artificial water channel membranes

Abstract

Synthetic polymer membranes, critical to diverse energy-efficient separations, are subject to permeability-selectivity trade-offs that decrease their overall efficacy. These trade-offs are due to structural variations (e.g., broad pore size distributions) in both nonporous membranes used for Angstrom-scale separations and porous membranes used for nano to micron-scale separations. Biological membranes utilize well-defined Angstrom-scale pores to provide exceptional transport properties and can be used as inspiration to overcome this trade-off. Here, we present a comprehensive demonstration of such a bioinspired approach based on pillar[5]arene artificial water channels, resulting in artificial water channel-based block copolymer membranes. These membranes have a sharp selectivity profile with a molecular weight cutoff of ~ 500 Da, a size range challenging to achieve with current membranes, while achieving a large improvement in permeability (~65 L m−2 h−1 bar−1 compared with 4–7 L m−2 h−1 bar−1) over similarly rated commercial membranes.

Biomimetic and bioinspired membranes for water purification: A critical review and future directions

“…Ideally, artificial channels can be synthesized using simple chemistry and are compatible with various solvents which make them convenient to synthesize. There has been an increase in recent years in studies discussing the design considerations, challenges encountered, and performance of membranes with artificial water channels [132,135,[138][139][140][141][142][143][144][145][146]. There are mainly two types of artificial channel types: self-assembling channels and unimolecular channels [135].…”

“…Another challenge is scalability of current approaches to synthesize biomimetic membranes on a large scale . Along with the work going on in the field of biomimetic membranes based on aquaporins, there has been an increase in the research associated with bioinspired materials . A number of artificial structures with similar structure–function relationships of aquaporins have been introduced and studied in the recent years.…”

Bioinspired nano-ordered liquid membrane for precise molecular separation

“…20 On the other hand, driven by intermolecular forces, bilayerspanning helices are assembled into versatile membrane proteins with N-and C-termini heading towards the cytosol, and these specialized membrane proteins are featured with well-de ned angstrom-scale channels and chemical functionality, 21,22 which synergistically combine size, charge, van der Waals, and other speci c binding interactions to achieve the selective and super-fast transport of target species. 23,24 For example, the AQP within cellular membrane exhibits a high permeability of 3 × 10 9 H 2 O molecules per second per AQP subunit but completely excludes all ionic species; 25 the CO 2 permeability can reach up to 120000 molecules per second per AQP subunit; 26 the potassium permeation rate is ~ 10 8 ions/s with a super high potassium/ sodium ion selectivity of ~ 1000. 2 The elegant structure and unprecedented performances of cellular membranes provide archetypes and grant germane inspirations for the design of highly e cient membranes for sub-angstrom/angstromscale ion or molecule separations.…”

“…31,32 In contrast, the self-assembling channels are constructed from selfassembly of small building blocks by weak intermolecular forces such as hydrophobic interactions or hydrogen bonding, 33,34 which offer advantages of chemical diversity, precise control of channel architecture and easy fabrication. 24,27 However, most reported bioinspired membranes with arti cial channel are small-membrane vesicles with diameter of ∼200 nm, meanwhile the low-density channels often result in low separation performances. 35 Therefore, novel bioinspired membrane with plenty of transport channels as well as cost-and process-e cient membrane construction strategy are still highly needed yet challenging, particularly when considering the fabrication of scalable membranes for practical applications.…”

On the perfect diameter condition to optimize the antibiotic nanoencapsulation: case of gramicidin

“…We can quote, the sea water desalinization [16] or filtering ions like dialysis applications [17]. The main problem is to create high permeability nanofilters while keeping their selectivity and without an excessive energy intake [18][19][20][21][22]. On the other ways, the perfect conditions to encapsulate ionic channel need to develop specific hydrophobic nanopore whose structural properties can reproduce at most the biological media where the ionic channels are stable [23][24].…”