Modern chemical synthesis often requires special environmental factors, such as high pressure, high temperature, chemical catalysts, or an oxygen-free atmosphere, just to name a few. Aside from the energy requirements, which can get expensive monetarily, the chemical requirements can get expensive environmentally in the case of an accident or spill.
Mechanochemistry eliminates some of these problems, effecting chemical reactions without the need for high-temperature or -pressure reaction chambers.
In recent years, mechanochemical ball milling has been able to produce complex chemical compounds, such as the metal-organic framework ZIF-8, from simple non-toxic components. Ball milling is essentially a rapidly vibrating container into which is put the reactants and steel balls.
The balls collide perhaps hundreds or thousands of times per second, compressing the reactants between each ball in an instant of extreme pressure and temperature. These myriad collisions are what make the ball mill functional, inexpensive, and environmentally friendly.
The moment of collision in mechanochemistry, and the actual process on a molecular scale has, until now, been difficult to observe, but Tomislav Friščić of McGill University, in collaboration with the University of Zagreb in Croatia, and the University of Cambridge, the Max-Planck-Institute for Solid State Research in Stuttgart, Germany, and the European Synchrotron Radiation Facility (ESRF) in Grenoble, France, has succeeded.
Using high-energy x-rays, Friščić was able to observe, in real time, the chemical reactions as they occurred inside the ball mill, without disturbing the process. “When we set out to study these reactions, the challenge was to observe the entire reaction without disturbing it, in particular the short-lived intermediates that appear and disappear under continuous impact in less than a minute,” says Friščić.
The new observation method can be used to improve mechanochemistry processes in practically any industry, making a greener, and more available, chemical method than current models.