Screen printing directed synthesis of covalent organic framework membranes with water sieving property

Abstract

An effective approach of screen printing has been developed to direct the synthesis of continuous COF membranes. The prepared membranes exhibit fast and selective water permeation properties.

Polycrystalline Covalent Organic Framework Films Act as Adsorbents, Not Membranes

“…These pellets were used to study dye uptake in flow. The most effective separations reported to date have been achieved using thick (5 μm–1 mm), polycrystalline slabs of COF powder. ,− To mirror these features while ensuring maximal material quality, 100 mg of TAPB-PDA COF powder ( S BET > 2000 m 2 g –1 , Figure S10) was briefly compressed between two polyester discs using a hydraulic press, forming a COF pellet suitable for flow studies. The resulting disc-shaped COF pellets were approximately 350 μm thick and 2.5 cm in diameter, a size selected to fit a stainless-steel filter housing.…”

“…Covalent organic frameworks (COFs) are permanently porous, crystalline polymers with predictable structures obtained by reacting geometrically constrained nodes and linkers to form networks of well-defined pores. − Changes in the monomer structure enable tuning of the pore size, topology, dimensionality, and linkage chemistry, , offering a rational means to impart emergent properties of interest for energy storage, − catalysis, , electronics, − sensing, , gas storage, and molecular separations. − Of the many proposed applications for COFs, rationally designed membranes with uniform porosity are among the most promising. , So far, tested COF separation membranes vary in material quality and can be divided into two categories. The first are thin films (<500 nm) with little or no apparent crystallinity, which are obtained by polymerizing monomers at liquid–liquid, liquid–solid, or liquid–air interfaces. ,− These films exhibit low water permeability (typically <50 L m –1 bar –1 h –1 ) and have shown separations of dyes ,,,− and salt solutions. ,− , The second category of COF membranes are obtained as thick films or solids using typical solvothermal or interfacial polymerization methods and are effectively polycrystalline powders fused into arbitrary shapes. ,− These forms often exhibit higher water permeability (>50 L m –1 bar –1 h –1 ) and have been used to separate organic dyes, ,− , proteins, bacteria, salts, and nanoparticles . Th...…”

“…The first are thin films (<500 nm) with little or no apparent crystallinity, which are obtained by polymerizing monomers at liquid–liquid, liquid–solid, or liquid–air interfaces. ,− These films exhibit low water permeability (typically <50 L m –1 bar –1 h –1 ) and have shown separations of dyes ,,,− and salt solutions. ,− , The second category of COF membranes are obtained as thick films or solids using typical solvothermal or interfacial polymerization methods and are effectively polycrystalline powders fused into arbitrary shapes. ,− These forms often exhibit higher water permeability (>50 L m –1 bar –1 h –1 ) and have been used to separate organic dyes, ,− , proteins, bacteria, salts, and nanoparticles . The separation capabilities of both categories of COF membranes have been attributed to a size-based sieving mechanism through the micropores or mesopores defined by the COF lattice (see Tables S1 and S2 for an overview of reported COF membranes and transport properties). ,,− …”

“…In the case of amorphous thin films, ,− the expected periodicity is ambiguous or not present. For the thicker polycrystalline solids, ,− which display some degree of crystalline ordering, claims of size-based sieving are similarly difficult to rationalize. These materials are comprised of unoriented nanoscale crystalline domains.…”

Synthesis of Thin Film of a Three‐Dimensional Covalent Organic Framework as Anti‐counterfeiting Label

“…[ 14 ] Recently, thin films of 2D COFs have been reported through interfacial synthesis at a gas‐liquid interface, [ 15‐16 ] liquid‐ liquid interface, [ 17 ] liquid‐solid interface, [ 18 ] spin coating, [ 19 ] microwave‐assisted synthesis, [ 20 ] and screen printing. [ 21 ] Some of the films, especially those gained at liquid‐containing interfaces could be readily transferred onto arbitrary substrates (including electrodes), which facilitated their integration in devices. These films have shown great promise in nanofiltration, [ 16,22 ] molecular separation, [ 18 ] photochemical sensing, [ 23 ] anion transport, [ 24 ] heat conduction, [ 25 ] and proton conduction.…”