A crystal with sponge-like properties
At the synchrotron SOLEIL, researchers come to study a material with astonishing properties: a powder, each grain of which is made up of molecules organized in the form of crystals which, at the nanometric scale, behave like sponges. These sponges absorb hydrogen in particular, and could be useful, for example, in designing the fuel tanks for tomorrow's hydrogen-powered cars.
Autumn 2024: a look back at this research
It’s 2014, on the CRISTAL beamline at the synchrotron SOLEIL. When PhD student Damien Foucher exposes his samples to the X-rays produced by this beamline, he is conducting fundamental research. He aims to study a strange molecule: a crystalline structure with holes, or pores, in which other molecules, such as water, can be captured.
This work, taken up by chemist Christian Serre, is part of the vast field of "MOFs," or Metal-Organic Frameworks. These are porous and flexible solids, whose pores act as particularly interesting traps for applications that require capturing other molecules.
Christian Serre recalls: "MOFs were discovered in the 1990s and literally exploded in the 2000s, with a first application enabling the capture of carbon dioxide from cement plant emissions." Since then, this molecular butterfly net has been the subject of extensive research worldwide.
For instance, if we consider hydrogen, a gas of great current interest, some MOFs can be used to purify it, store it, or even separate it from its isotopes (deuterium, tritium) inside nuclear power plants.
However, for the pores of a MOF to be empty and the material "activated," they first need to be "cleaned." Paradoxically, these gaps are often occupied by organic molecules necessary for the very synthesis of the MOFs. Typically, these molecules are removed through calcination—a process that doesn't easily allow for industrial-scale production. In 2022, Christian Serre developed an alternative method using a "green" solvent, which allows the activation of several hundred grams of MOF—enabling a shift to larger-scale production. A patent for this process has been filed with the CNRS.
In the same vein, Christian Serre founded a startup1 that develops efficient materials to improve air quality, particularly by removing indoor air pollutants like formaldehydes, which are recognized carcinogens. MOFs are thus finding roles in surprising applications. "The U.S. Army even designed textiles for military uniforms that can neutralize gaseous neurotoxic agents," the chemist notes.
To deepen the understanding of these "crystal sponges," Christian Serre frequently uses a versatile characterization tool: the synchrotron. For eight years, he has come to PROXIMA 2 at SOLEIL, working closely with William Shepard, the beamline manager, to analyze the new crystalline structures he develops. On the ROCK beamline, he focuses on the production of hydrogen from water photolysis. And finally, the CRISTAL beamline allows him to study what happens at the level of powdered MOFs. Promising MOFs among many others...
1 - Squair Tech, https://www.squair.tech/
Related publications
Benzaqui, M., Wahiduzzaman, M., Zhao, H., Hasan, M.R., Steenhaut, T., Saad, A., Marrot, J., Normand, P., Grenèche, J.M., Heymans, N., De Weireld, G., Tissot, A., Shepard, W.E., Filinchuk, Y., Hermans, S., Carn, F., Malankowska, M., Téllez Ariso, C., Coronas, J., Maurin, G., Steunou, N., Serre, C. "A Robust Eco-compatible Microporous Iron Coordination Polymer for CO2 capture" Journal of Materials Chemistry A., 10(15): 8535-8545. (2022).
Wang, S., Xhaferaj, N., Wahiduzzaman, M., Oyekan, K., Li, X., Wei, K., Zheng, B., Tissot, A., Marrot, J., Shepard, W.E., Martineau-Corcos, C., Filinchuk, Y., Tan, K., Maurin, G., Serre, C. "Engineering Structural Dynamics of Zirconium Metal-Organic Frameworks Based on Natural C4-linkers" Journal of the American Chemical Society., 141(43): 17207-17216. (2019).
Wang, S., Cabrero-Antonino, M., Navalón, S., Cao, C., Tissot, A., Dovgaliuk, I., Marrot, J., Martineau-Corcos, C., Yu, L., Wang, H., Shepard, W., García, H., Serre, C. "A Robust Titanium Isophthalate Metal-Organic Framework for Visible-Light Photocatalytic CO2 Methanation" Chem., 6(12): 3409-3427. (2020).