Flexible Ionic Conjugated Microporous Polymer Membranes for Fast and Selective Ion Transport

Abstract

Membranes with fast and selective ion transport have great potential for use in water-and energy-related applications. The structure and material design of the membranes play a key role in improving their performance. Conjugated microporous polymers (CMPs) as emerging membrane materials have shown uniform pore size, high surface area, and excellent chemical stability, but their mechanical properties are poor due to their brittleness. Herein, a flexible ionic CMP membrane with precisely tailored pore architecture and chemistry prepared by a coelectropolymerization (COEP) strategy is reported. The structure contains rigid monomers to maintain structural uniformity and flexible and charged monomers to enhance mechanical flexibility and improve ion selectivity by combining precise size sieving and Donnan effect. The resulting 40 nm thick CMP membranes show equivalent ion conductance compared to the commercial Nafion 117 membrane, but an order of magnitude higher ion selectivity for ion systems such as K + /Mg 2+ and Li + /Mg 2+ .

Conjugated microporous polymer membranes for light-gated ion transport

“…The obtained membranes were immersed in a mixture solution of dichloromethane and acetonitrile overnight to remove electrolytes and unreacted monomers. Then, freestanding azo-CMP membranes were obtained from ITO glass using the reported surface tension–assisted transfer method ( 28 ). These membranes can be easily transferred on potential energy surface (PES) porous support (0.22 μm in pore size) for further testing and applications.…”

“…Conjugated microporous polymers (CMPs) are a unique class of porous organic materials with -conjugation structures and intrinsic micropores (23)(24)(25)(26). The membranes made from CMPs by the electropolymerization method in our previous works (27)(28)(29) have shown high porosity, uniform pore size, and impressive molecular/ion transport and sieving performance. In addition, the design of CMP monomers on molecular level could yield immense opportunities for the customization of functionalized membranes (27,28,30,31).…”

“…The membranes made from CMPs by the electropolymerization method in our previous works ( 27 – 29 ) have shown high porosity, uniform pore size, and impressive molecular/ion transport and sieving performance. In addition, the design of CMP monomers on molecular level could yield immense opportunities for the customization of functionalized membranes ( 27 , 28 , 30 , 31 ). The structure and thickness of CMPs membranes can be easily and precisely controlled in nanometer scale by the electropolymerization strategy ( 27 – 29 ).…”

“…In addition, the design of CMP monomers on molecular level could yield immense opportunities for the customization of functionalized membranes (27,28,30,31). The structure and thickness of CMPs membranes can be easily and precisely controlled in nanometer scale by the electropolymerization strategy (27)(28)(29). All these advantages make CMPs one of the best candidates as the synthetic materials for the precise construction of smart ion channel membranes.…”

Highly efficient monovalent ion transport enabled by ionic crosslinking‐induced nanochannels

“…However, these membranes are difficult to fabricate, even with controllable scalability, which hinders their industrial application 9 . Polymeric membranes have advantages in fabrication processability; however, conventional linear polymer chains tend to form broad pore size distributions, leading to low ionic selectivity 10 . Hence, engineering an ideal polymeric membrane with strengthened charge‐governed repulsion derived from surface chemistry while retaining its relatively loose pore channels remains a long‐standing objective for the advancement of high‐accuracy ionic transmembrane transport.…”