Meeting the UN Sustainable Development Goals with Mechanochemistry

Abstract

Chemistry traditionally relies on reactions in solution, but this method is increasingly problematic due to the scale of chemical processes and their economic and environmental impact. Handling residual chemical waste, including solvents, incurs significant costs and environmental pressure. Conversely, novel chemical approaches are needed to address pressing societal issues such as climate change, energy scarcity, food insecurity, and waste pollution. Mechanochemistry, a sustainable chemistry discipline that uses mechanical action to induce chemical reactivity without bulk solvents, is a hot topic in academic research on sustainable and green chemistry. Given its fundamentally different working principles from solution chemistry, mechanochemistry offers more efficient chemical processes and the opportunity to design new chemical reactions. Mechanochemistry has a profound impact on many urgent issues facing our society and it is now necessary to use mechanochemistry to address them. This Minireview aims to provide a guide for using mechanochemistry to meet the United Nations (UN) Sustainable Development Goals (SDGs), thereby contributing to a prosperous society. Detailed analysis shows that mechanochemistry connects with most UN SDGs and offers more cost-efficiency than other approaches together with a superior environmental performance.

From an Ancient Tool to a Modern Discipline

The term “mechanochemistry” was coined by Wilhelm Ostwald in 1919.1 He defined mechanochemistry as a branch of chemistry that studies chemical and physical changes of substances in any aggregation state resulting from mechanical action. Different definitions of mechanochemistry are currently used.2 However, mechanochemistry has been around since ancient times and people have used it to start a fire by rubbing two stones together or creating friction with a wooden stick.3 Grinding has also been used for millennia to prepare food and perform (al)chemical reactions.4 The first documented mechanochemical reaction was reported in the fourth century BC in the book of Theophrastus, a student of Aristotle. He described the reduction of cinnabar to elemental mercury and chalcocite in a mortar and pestle made of copper using catalytic amounts of vinegar.5 Notably, the need for copper and vinegar is not immediately apparent, the reaction does not work in stone or iron equipment, and it is inefficient when water is used as a liquid additive. However, performing chemistry by mechanical action has historically been overshadowed by performing it in solution, perhaps influenced by “no coopora nisi fluida”, meaning “no reaction occurs in the absence of solvent”.6

The recent renaissance of mechanochemistry is a result of the green chemistry movement,7 as mechanochemistry fits well with the 12 principles of green chemistry.8 Manual grinding experiments are now performed in mills, extruders, and resonant acoustic mixers that generate different types of mechanical forces (Figure 1a).9 Mechanochemistry as a synthetic tool has found application in all types of chemistry,10-19 and various types of in situ monitoring methods provided insights into mechanochemical processes kinetics, and mechanisms.20, 21 The latest developments in chemical reactivity are new approaches combining mechanochemical action with other energy sources. These include thermo-mechanochemical, photo-mechanochemical, sono-mechanochemical, and electro-mechanochemical methods, which offer new possibilities for chemical reactivity.22

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Dr. Jasna Alić, Dr. Moritz-Caspar Schlegel, Priv.-Doz. Dr. Franziska Emmerling, Dr. Tomislav Stolar, Meeting the UN Sustainable Development Goals with Mechanochemistry, First published: 18 September 2024 https://doi.org/10.1002/anie.202414745