Dawei Feng, the Y. Austin Chang Assistant Professor in the Department of Materials Science & Engineering at the University of Wisconsin-Madison, has spent the last decade investigating metal-organic materials, or MOMs, which combine two types of materials that rarely bond with one another. In particular, Feng has studied a variety of MOMs called metal-organic frameworks, porous solid materials that bond together molecules of metals with organic molecular linkages. These materials have shown promise in gas and water purification, carbon sequestration, catalysis and other applications.
Now, with the aid of a National Science Foundation CAREER Award, Feng wants to investigate a whole new category of MOMs; in fact, he’s aiming to create a combination never explored before. “The biggest point is that we are trying to construct a new class of materials out of nowhere,” says Feng. “But that means screening materials and combining them together to see what we get.”
With a few important exceptions, most metal-organic materials act as electrical insulators. But in this project, Feng hopes to layer atomically thin metals with the assistance of organic bridges to produce a new class of 2D structures with semiconductive properties, namely multiatomic layered eMOMs.
Feng’s approach to this challenge is to use coordination chemistry mimicking the property and structure of many conventional 2D semiconductive inorganic materials. While the core inorganic layer provides desired electronic properties, highly tunable organic tails could microtune those properties and communicate with external species when needed.
The concept is simple, but it all depends on matching the right organic material, or ligand, with the right metal species—and there are thousands of potential combinations. “It’s basically how do we find a good match between the metal and the organic,” Feng says. “Typically, I use transition metal species, which have a good energetic match with the organic ligands to establish an effective ‘electron sharing’ bonding mode.”
To assess all those combinations, Feng will work with data science collaborators, including Harvey D. Spangler Professor of Materials Science & Engineering Dane Morgan, to develop algorithms that will speed the evaluation process along. He will also work with other collaborators throughout UW-Madison to analyze and characterize the new materials.
So what will these multilayer-eMOMs be good for? Feng says he can see some of them being useful in sensing applications and, because they are so thin and can be easily functionalized, wearable technology. They could also be precursors for fabrication of inorganic thin film semiconductors. But those are just guesses. This is true “blue-sky” fundamental science and at this point Feng says it’s hard to predict where these types of materials might end up.
“We will do analysis and high-throughput synthesis to screen all different combinations of these materials, then we’ll measure their structure, electronic properties and some other chemical and physical properties,” he says. “It’s all about possibility. We could end up with something, or we could end up with nothing.”
As part of the CAREER award, Feng is also developing an educational module for middle schoolers he’s calling Make MOFs at Home, which could be performed in-person or remotely. Using products most students can find at home or the grocery store, they will be able to experiment with their own version of metal-organic materials that can sequester CO2 or purify water.