Controlling the Selectivity of Conjugated Microporous Polymer Membrane for Efficient Organic Solvent Nanofiltration

Abstract

To realize selective separation of important small molecules in organic solvents with high permeability is highly desired but not attained yet, because it requires stringent control over selectivity in nanofiltration membranes. Here, a thiophene-containing conjugated microporous polymer membrane, in which the pore size is finely tuned at the angstrom scale through postoxidation of the thiophene moieties, is reported. The successful modification is confirmed by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and water contact angle, leading to obvious pore size reduction evidenced by nitrogen adsorption. Upon postmodification, the selectivity of the membrane can be effectively controlled. In the pristine membrane, the methanol permeance reaches 32 liters per square meter per hour per bar (L m −2 h −1 bar −1 ) with a molecular weight cut-off (MWCO) of 800 g mol −1 . Significantly, after in situ postmodification of thiophene moieties, the largest pore size is reduced from 1.73 to 1.48 nm, giving rise to a remarkable decrease of MWCO from 800 to 500 g mol −1 , while the permeance of methanol still maintains as high as 21 L m −2 h −1 bar −1 .

Photodriven Active Ion Transport Through a Janus Microporous Membrane

“…The Janus microporous membrane was fabricated by the sequential electrochemical polymerization of a thiophene‐containing CMP (TTB‐CMP) layer, followed by spin‐coating another layer of rGO nanosheets (Figure a). Briefly, the TTB‐CMP layer was firstly prepared on the indium tin oxide (ITO) substrate through electrochemical polymerization of TTB monomers . The detailed electrochemical polymerization process and Fourier transform infrared spectroscopy (FTIR) spectrum of the linkage chemistry are described in Figure S1 (Supporting Information).…”

“…The thickness of the TTB‐CMP layer was measured by atomic force microscopy (AFM) imaging and the corresponding height profile (Figures a,b) and the thickness can be tuned from 27 to 164 nm by controlling the electrochemical polymerization cycles (Supporting Information, Figure S2c). According to our previous N 2 adsorption experiments, the pore size of the as‐fabricated TTB‐CMP layer centered at 1.47 and 1.73 nm . After washing and drying, the rGO suspension was spin‐coated on the TTB‐CMP layer.…”

“…[15] On the other hand, both the topological structure and pore size of CMPs are easily tuned through molecular engineering, [16] enabling efficient molecular transport and sieving. [17] Inspired by the ion pumps in nature and the electron-hole separation of the heterojunction structure in conventional photovoltaic devices, [18] we suggest a new strategy to create a transmembrane electric field in a solid-state Janus microporous membrane composed of reduced graphene oxide (rGO) and CMP to realize photovoltaicinduced active ion transport. By simply combining the rGO and CMP layer, a donor-acceptor interface is conveniently formed with a large area.…”

Graphene‐Based Advanced Membrane Applications in Organic Solvent Nanofiltration

“…[ 32–34 ] However, the strong adsorption of organic solvents onto polymeric membranes has hindered their applications in future industries; this is because the high sorption of organic solvents (up to 50 wt%) together with the potential membrane disintegration in organic solvents can negatively affect the overall stability of membranes. [ 29,35–39 ] Thus, efforts have been exerted to use tough glassy polymers that are composed of condensed aromatic rings (e.g., polybenzimidazoles, [ 40–42 ] polyacrylates, [ 43 ] polymers of intrinsic microporosity, [ 44–47 ] and perfluorinated polymers [ 48 ] ) to fabricate membranes. Nevertheless, the inherent limitations of polymeric membranes, such as plasticization, [ 46,49 ] physical aging, [ 50,51 ] and the tradeoff relationship between permeance and rejection, [ 29,43 ] remain highly challenging in the application of polymeric membranes in OSN processes.…”

Effect of Porous and Nonporous Nanostructures on the Permeance of Positively Charged Nanofilm Composite Membranes

“…A different approach to reducing the thickness of the nanofilm separation layer may produce higher liquid permeance. [41][42][43][44][45] Thus, introducing nanoporous materials in the ultrathin separation layer may even produce higher liquid permeance. Indeed, through introducing voids and interlayer composite structures, high flux composite membranes are also developed recently.…”