Will mechanochemistry come into its own?

Arguably, early humans first practiced mechanochemistry some 400,000 years ago, when they used friction to create fire. In ancient Greece, Theophrastus noted that cinnabar could be reduced to mercury through the mechanical process of grinding with mortar and pestle.

These days, mechanochemistry has a more modern spin. It is touted both as a way of conducting existing reactions without the use of solvents and as a way of carrying out entirely new chemical processes. Interest among academic chemists is high, as evidenced by an increasing number of journal articles, but a relatively low number of patent filings is a sign that widespread commercial adoption lags behind.

A recent analysis by CAS, a division of the American Chemical Society that specializes in scientific-knowledge management, defines mechanochemistry as a process in which mechanical forces such as grinding, milling, and shearing drive chemical transformations. (C&EN is published by ACS.) Milling is the most common way to carry out mechanochemical reactions, followed by grinding, ultrasonication, and reactive extrusion.

In 2019, on the 100th anniversary of its founding, the International Union of Pure and Applied Chemistry (IUPAC) identified reactive extrusion as one of “ten chemical innovations that will change our world.” An IUPAC article on the topic noted that classic mechanochemical processes like grinding and milling must occur in batches, whereas extrusion methods using screws can allow the solvent-free reactions to operate continuously.

Although mechanochemistry is now mostly the province of academia, a number of companies, many based in Japan, have been actively patenting mechanochemical technology.

The leading patentee, Fujifilm, has received several patents on mechanochemical methods of polishing. One patent, for example, describes a chemical mechanical method of polishing a modified polysilicon wafer during semiconductor fabrication. Panasonic, another Japanese firm with multiple mechanochemistry patents, describes the synthesis of a halide battery electrolyte with mechanochemical treatment using a ball mill.

The Canadian firm Carbon Upcycling Technologies patented a method for using mechanochemistry to activate phyllosilicate minerals and other materials to sequester carbon dioxide. Another patent from Carbon Upcycling describes a method of using mechanochemistry to activate low-kaolinite feedstocks and combine them with materials such as asphalt, cement, geopolymers, and other polymers to form a concrete.

James Mack, a chemistry professor at the University of Cincinnati, is convinced enough of the industrial potential of mechanochemistry that in 2022 he formed a company, Cinthesis Solutions, to pursue it. Mack says Cinthesis helps companies assess whether reactions they conduct with solvents and at high temperatures can be conducted in, say, a ball mill or a twin-screw extruder under more-sustainable conditions and with less labor.

As a scientist, Mack is part of the US National Science Foundation’s Center for the Mechanical Control of Chemistry at Texas A&M University. There, he says, chemists and mechanical engineers get together to build new instruments and machines to do mechanochemical reactions. “This NSF-funded center’s goal is to provide the scientific community with an easy on-ramp to do mechanochemical research,” Mack says.

Mack argues that any resistance to mechanochemistry in the chemistry world is cultural, not scientific. “It is actually not hard to convince companies to convert to mechanochemistry; it is hard to convince scientists to do so,” he says.

The story of mechanochemistry, Mack predicts, will be similar to that of continental drift, which was dismissed by the geology community when Alfred Wegener proposed it in 1912. Today, of course, continental drift and its underlying mechanism, plate tectonics, are foundational components of every geology curriculum.

“The core challenge,” Mack says, “is not the chemistry itself, but rather that many people see this way of doing chemistry as a threat to the cultural norms of the field.”

Eye on mechanochemistry

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How mechanochemistry works

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Popular transformations

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Promising industries

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Corporate captains

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China leaders

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Mechanochemistry mavens

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