New design! An ion conduction membrane with K+ efficient transport capability was successfully developed

Membrane materials with fast ion selective transport have broad application prospects in industrial separation, energy and other applications. While these applications often involve the separation of specific ions from complex mixtures, it is critical to design membrane materials with efficient ionic selective conduction.

Recently, the team of Li Xianxian, a researcher at the Dalian Institute of Chemical Physics, Chinese Academy of Sciences, and the team of researcher Li Guohui have made new progress in the structural design and research of ion conduction membrane materials. Through the design of the ion transport channel in the membrane, the team achieved K+ rapid transport, and studied and discussed the membrane structure and ion transport mechanism in detail. The results were published in Nature Communications.

Schematic diagram of ion conduction membrane (photo provided by Dalian Chemical)

In this work, the team constructed a membrane material with a controlled ion transport channel by coordinating metal ions with polybenzimidazole. The results show that Zn2+ and polybenzimidazole PBI coordinate to obtain a uniform polymer coordination network, forming a continuous water channel and exposing more polar groups, which promotes the rapid transport of K+. Subsequently, the team calculated the transport behavior of K+ in the polymer network through molecular dynamics simulations, revealing that K+ interacts with -N= on the polymer chain and is close to the oxygenated ether bond of the segment, thereby rapidly passing through the polymer membrane.

At the same time, the free volume of the coordination membrane increases, forming sub-nanometer molecular channels. The physical confinement of nanochannels and the electrostatic interaction of the membrane make the migration of K+ in concentrated salt and alkali solutions not affected by the concentration of the solution, and the migration number is as high as 0.9, which is comparable to cation exchange membranes. The assembly of alkaline zinc-iron flow battery using K+ high-efficiency ion conduction membrane can effectively alleviate the problem of water migration caused by the imbalance of ion strength caused by zinc deposition during battery operation.

This study provides a strategy for regulating the polymer chain structure through metal ion coordination to regulate the ion transport characteristics of polymer membranes, and also deepens the understanding of the membrane ion transport mechanism of metal-coordinated polymers. (Source: Sun Danning, China Science News)

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