November 11, 2022 Reviewed by Alex Smith
A research team led by Cheng Gu of South China University of Technology and Susumu Kitagawa of Kyoto University’s Institute of Cellular Materials Science (iCeMS) has developed a material that can successfully separate l ‘heavy water from normal water at room temperature.
The incorporation of dragonfly-shaped gate molecules into PCPs/MOFs makes it 100 times more efficient than before to separate water from heavy water, which has been difficult to separate due to their similar properties. Image credit: ©️Mindy Takamiya/Kyoto University iCeMS)
This process has been very difficult and time-consuming so far. The findings have implications for industrial processes that use multiple forms of the same molecule, including biological ones. The journal Nature published the researchers’ findings.
Isotopologues are molecules with the same chemical formula and similar bonding patterns, but at least one of their atoms differs from the parent molecule in terms of neutron count. For example, two hydrogen atoms and one oxygen atom combine to form the water molecule (H2O).
Each hydrogen atom has a single proton in its nucleus and no neutrons. Deuterium (D) atoms, on the other hand, are hydrogen isotopes with nuclei containing one proton and one neutron in heavy water (D2O). Nuclear reactors, medical imaging and biological research make use of heavy water.
The isotopologues of water are among the most difficult to separate because their properties are so similar. Our work provided an unprecedented mechanism to separate water isotopologues using an adsorption-separation method.
Cheng Gu, materials scientist, South China University of Technology
Gu and chemist Susumu Kitagawa, along with colleagues, used a porous coordination polymer (PCP) made of copper as the basis for their separation technique. The metal nodes joined by organic bonds form the porous crystalline materials known as PCP. The team tested two PCPs made with various types of linkers.
Their PCPs are particularly crucial for the separation of isotopologues, as the bonds are rotated when heated to a moderate temperature. As a gate, this flipping action allows molecules to move freely between the “cages” of the PCP. The material becomes immobile as it cools.
When the researchers exposed their “dynamic flip-flop crystals” to a vapor containing a mixture of normal, heavy and semi-heavy water and then heated it slightly, they found that normal water absorbed much faster than the other two isotopologues. . Crucially, this procedure was carried out at temperatures close to room temperature.
The adsorptive separation of water isotopologues in our work is substantially superior to conventional methods due to the very high selectivity at room temperature. We are optimistic that new materials guided by our work will be developed to separate other isotopologues.
Susumu Kitagawa, Institute of Cellular Materials Science, Kyoto University
Journal reference:
Su, Y., et al. (2022) Separation of water isotopologues using diffusion-regulating porous materials. Nature. doi:10.1038/s41586-022-05310-y.
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