Tomislav Friscic calls it “lazy man’s chemistry.” At the 23rd Congress and General Assembly of the International Union of Crystallography in Montreal this past August, Friscic, a McGill University chemist, described experiments where he combined simple, mineral-like metal oxides with organic derivatives of oxalic acid, then simply left the mixtures at room temperature and high humidity. When he checked back a week later, there was a modest amount of a microporous metal-organic framework — the types of modern materials that are now finding applications in gas storage and chemical sensors and are even thought suitable as light-harvesting materials in solar panel construction.
“We are trying to mimic what nature does, in the so-called mineral weathering reactions that transform intractable minerals into more soluble and reactive ones over the course of centuries,” Friscic says. “You can use similar, solid-state chemistry to make these metal-organic materials much easier and cheaper, without the use of aggressive solvents or high temperatures.”
More specifically, Friscic specializes in finding simple ways to chemically or mechanically accelerate the otherwise very slow natural weathering processes driven by organisms such as lichen, which employ simple organic molecules such as oxalic acid to extract and separate metals contained in minerals. “We perceive this as a viable way of working with minerals and replacing the very dirty aspects of mineral processing,” he says. Apart from reducing the processes’ environmental impact, this approach can significantly reduce the energy required to extract desired components from ores, such as the increasingly valuable rare earths used in a variety of high-tech devices.
Currently, Friscic’s “accelerated aging” approach to extraction has been able to yield hundreds of grams of materials at a time and he foresees a commercial future for this method. His inspiration, Friscic says, is also in the ancient processes for making pigments, such as lead white, which was made through similar processing until the early 20th century. “We see no limitation with scale-up,” he says. “We have seen some possibilities for solvent-free separation of important mineral mixtures, not only for the basic metals copper, zinc, lead but also for lanthanides and more noble metals.”