Molecularly-porous ultrathin membranes for highly selective organic solvent nanofiltration

Abstract

Engineering membranes for molecular separation in organic solvents is still a big challenge. When the selectivity increases, the permeability tends to drastically decrease, increasing the energy demands for the separation process. Ideally, organic solvent nanofiltration membranes should be thin to enhance the permeant transport, have a well-tailored nanoporosity and high stability in harsh solvents. Here, we introduce a trianglamine macrocycle as a molecular building block for cross-linked membranes, prepared by facile interfacial polymerization, for high-performance selective separations. The membranes were prepared via a two-in-one strategy, enabled by the amine macrocycle, by simultaneously reducing the thickness of the thin-film layers (<10 nm) and introducing permanent intrinsic porosity within the membrane (6.3 Å). This translates into a superior separation performance for nanofiltration operation, both in polar and apolar solvents. The hyper-cross-linked network significantly improved the stability in various organic solvents, while the amine host macrocycle provided specific size and charge molecular recognition for selective guest molecules separation. By employing easily customized molecular hosts in ultrathin membranes, we can significantly tailor the selectivity on-demand without compromising the overall permeability of the system.

Engineering membranes with macrocycles for precise molecular separations

“…9c). 156 The multiple reactive sites of trianglamine led to a highly crosslinked ultrathin selective layer (<10 nm). Permeances as high as 40 L m -2 h -1 bar -1 were demonstrated with molecular weight cut-off around 450 g mol −1 .…”

“…For racemic separation, the rejection of D-Leucine is 31% compared to 17% rejection for L-Leucine. 156…”

Porous Organic Compounds – Small Pores on the Rise

“…used terephthaloyl chloride (TPC) to prepare highly crosslinked membranes by interfacial polymerization with T2 L as monomer. The ultra‐thin, selective layer (<10 nm) with a small molecular weight cut‐off (around 450 g mol −1 ) was able to separate chiral solutes (amino acids) by chirality due to the specific pore size and chiral nature exhibited by the trianglamine moiety [25b] . During the production of this minireview, studies on m ‐xylene separation, [25e] and haloalkane isomer separation [25f] appeared.…”

2D Metal‐Organic Framework‐Based Thin‐Film Nanocomposite Membranes for Reverse Osmosis and Organic Solvent Nanofiltration

“…[17][18][19] Organic solvent nanofiltration (OSN) is an emerging application of membrane separations where TFC membranes also play an important role. [20,21] Nonetheless, membrane stability and permeability-selectivity tradeoff are the major obstacles that hinder the industrial applications of these membranes, in particular when resistance to harsh organic solvent is required. [22] Embedding solvent-resistant and microporous components into the polyamide layer might provide an effective approach to enhance membrane stability and permeability.…”