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Porous fluoropolymer separates water-soluble organics

Nanoporous material is the first to selectively pull dyes and other compounds from water based on their charge and size

by Stephen K. Ritter
November 21, 2016 | A version of this story appeared in Volume 94, Issue 46

Credit: Cafer T. Yavuz
A porous fluoropolymer (dark material in test tubes) selectively removes the dye methylene blue from water.
Reaction scheme shows formation of a polymer from tetrafluorohydroquinone, and its use to trap methylene blue from a test tube solution.
Credit: Cafer T. Yavuz
A porous fluoropolymer (dark material in test tubes) selectively removes the dye methylene blue from water.

Porous materials such as zeolites, metal organic frameworks, and nanocarbons are known for their ability to selectively interact with and separate chemical species having similar sizes and functional groups. But the ability to separate charged molecules of various sizes, especially when dissolved in water, has remained a challenge. A team led by Cafer T. Yavuz of Korea Advanced Institute of Science & Technology (KAIST) has now reported a microporous network fluoropolymer that can selectively separate cationic dyes and other charged molecules from mixtures of water-soluble organics (Nat. Commun. 2016, DOI: 10.1038/ncom​ms13377). The researchers first prepared an inexpensive new covalent organic polymer, dubbed COP-99, by treating commercially available tetrafluorohydroquinone with potassium carbonate (shown). They found that the material pulls modestly sized charged molecules such as the dye methylene blue out of water, but it isn’t capable of sequestering larger dye molecules such as rhodamine B or uncharged molecules such as bisphenol A. The key to the material’s selectivity is its restrictive pore size and the exposed fluorine atoms, Yavuz notes, which both create hydrophobic pores and provide strong electronegative forces attractive only to charged organics. The KAIST team envisions a range of applications, including water treatment to remove artificial dyes, pesticides, and prescription drugs.

A structure of a fluoropolymer.


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