Mechanochemistry: Fundamentals, applications and future

What maketh a pore? The formation of porosity in the solid-state Sven Grätz and Lars Borchardt Ruhr-Universität Bochum, Germany In the recent past, mechanochemical reactions inside ball mills have climbed their way back into general chemistry and material synthesis alike. As a green method, the future of this field is promising since the use of toxic solvents can be avoided while generally high selectivities and yields are maintained.[1]For the field of porous materials, by now a plethora of mechanochemical synthesis pathways have been reported. While amorphous materials like porous polymers [2] seem to be the logical results of these reactions, even crystalline materials like Metal-Organic-Frameworks [3] are obtainable in the destructive environment of a ball mill. This amongst many other observations let us to wonder how the formation of a pore is happening in these solid- state approaches. Common knowledge dictates the need for a porogen in order for permanent porosity to be formed. This is well understood in solution-based systems where the solvent, surfactant or template are used in this capacity. But what happens in the absence of one, two or all of those three components? How can the formation of persistent porosity be explained in those cases? Is the structure of the starting material governing this process or are reaction by-products responsible? And can the formation of porosity be tailored by adjusting the mechanochemical reaction parameters? [4] [5] In the presentation, I am going to elaborate on these and many other questions and discuss the similarities and differences between the solid-state and solution protocols for the synthesis of porous polymers. References 1. Friščić, T., Mottillo, C., & Titi, H. M. (2020). Mechanochemistry for synthesis. Angewandte Chemie, 132(3), 1030-1041. 2. Krusenbaum, A., Grätz, S., Tigineh, G., Borchardt, L., Kim, J.G., (2022) The Mechanochemical Synthesis of Polymers. Chemical Society Reviews, accepted 3. Głowniak, S., Szczęśniak, B., Choma, J., & Jaroniec, M. (2021). Mechanochemistry: Toward green synthesis of metal– organic frameworks. Materials Today, 46, 109-124. 4. Krusenbaum, A., Geisler, J., Kraus, F. J. L., Grätz, S., Höfler, M. V., Gutmann, T., & Borchardt, L. (2022). The mechanochemical Friedel-Crafts polymerization as a solvent-free cross-linking approach toward microporous polymers. Journal of Polymer Science, 60(1), 62-71. 5. Krusenbaum, A., Grätz, S., Bimmermann, S., Hutsch, S., & Borchardt, L. (2020). The mechanochemical Scholl reaction as a versatile synthesis tool for the solvent-free generation of microporous polymers. RSC Advances, 10(43), 25509-25516.

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