A new, biomass-based material developed by FAMU-FSU College of Engineering researchers can be used to repeatedly capture and release carbon dioxide.

The material is primarily made from lignin, an organic molecule that is a main component of wood and other plants, and it can take up carbon dioxide (CO2) from concentrated sources or directly from the air. The research was published by Advanced Materials.

“The beauty of this work is the ability to precisely control the capture and release of CO2 without high pressure or extreme temperatures,” said study co-author Hoyong Chung, an associate professor in the FAMU-FSU College of Engineering. “Our testing showed that this material’s structure stayed the same even after being used multiple times, making this a promising tool for mitigating carbon emissions.”

In previous research, Chung’s team developed a lignin and CO2-based polymer that represented a potential alternative to traditional petroleum-based plastic. This paper takes that research further, showing the possibility of reversing the process and of reusing the material to absorb CO2 again in the future.

Because it is found in plants, lignin is abundant and cheap, and it is often harvested as a byproduct from wood processing. Scientists are working to find new ways to use this natural resource.

One gram of the material developed by Chung’s team captured 47 milligrams — about 5% of the weight of the original material — of CO2 from a concentrated source and 26 milligrams from exposure to ambient air. The absorbed CO2 can be permanently sequestered, or it can be released for use in various applications, such as manufacturing, agriculture and others.

Researchers were surprised by the release mechanism. While using nuclear magnetic resonance spectroscopy to analyze a sample, they saw bubbles appear when the sample was heated.

“That sparked our curiosity,” Chung said. “What’s going on here? Why do we see these little bubbles every time we try to analyze this polymer?”

Further investigation revealed that heat was causing the material to release CO2. The researchers investigated the reaction and found that by controlling the heat applied to the sample, they were able to control the amount of CO2 released. They also showed the possibility of using that captured gas in other reactions.

It only takes temperatures of about 60 degrees Celsius at normal atmospheric pressure to release the CO2, meaning high temperatures and pressures aren’t necessary for the reuse process. This CO2 release temperature can be increased or decreased for different applications.

“This is like a sponge for CO2, absorbing it, releasing it and drying up so it can capture more,” Chung said. “It’s fascinating to see what is possible with this material.”

Postdoctoral researcher Arijit Ghorai was the lead author of the study.

This work was supported by the U.S. Department of Agriculture National Institute of Food and Agriculture.

Visit the Chung Research Group website for more information about this and other ongoing work.

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Modern life relies on plastic. This lightweight, adaptable product is a cornerstone of packaging, medical equipment, the aerospace and automotive industries and more. But plastic waste remains a problem as it degrades in landfills and pollutes oceans.

FAMU-FSU College of Engineering researchers have created a potential alternative to traditional petroleum-based plastic that is made from carbon dioxide (CO2) and lignin, a component of wood that is a low-cost byproduct of paper manufacturing and biofuel production. Their research was published in Advanced Functional Materials.

“Our study takes the harmful greenhouse gas CO2 and makes it into a useful raw material to produce degradable polymers or plastics,” said Hoyong Chung, an associate professor in chemical and biomedical engineering at the college. “We are not only reducing CO2 emissions, but we are producing a sustainable polymer product using the CO2.”

This study is the first to demonstrate the direct synthesis of what’s known as a cyclic carbonate monomer — a molecule made of carbon and oxygen atoms that can be linked with other molecules — made from CO2 and lignin.

By linking multiple monomers together, scientists can create synthetic polymers, long-chained molecules that can be designed to fill all manner of applications.

The material developed by Chung and his research team is fully degradable at the end of its life without producing microplastics and toxic substances. It can be synthesized at lower pressures and temperatures. And the polymer can be recycled without losing its original properties.

Using depolymerization, the researchers can convert polymers to pure monomers, which are the building blocks of polymers. This is the key to the high quality of the recycled material. The monomers can be recycled indefinitely and produce a high-quality polymer as good as the original, an improvement over previously developed and currently used polymer materials in which repeated heat exposure from melting reduces quality and allows for limited recycling.

“We can readily degrade the polymer via depolymerization, and the degraded product can synthesize the same polymer again,” Chung said. “This is more cost effective and keeps it from losing original properties of polymers over multiple recycling. This is considered a breakthrough in material science, as it enables the realization of a true circular economy.”

The newly developed material could be used for low-cost, short lifespan plastic products in such sectors as construction, agriculture, packaging, cosmetics, textiles, diapers and disposable kitchenware. With further development, Chung anticipates its use in highly specialized polymers for biomedical and energy storage applications.

The FSU Office of Commercialization provided valuable foundational support for Chung’s research. Support from an internal funding program helped previous work with lignin-based polymers, and with the help of the office, he has received patents for other polymer research.

The project was supported by federal funds awarded to the State of Florida from the United States Department of Agriculture, National Institute of Food and Agriculture and support from the FAMU-FSU College of Engineering. Postdoctoral researcher Arijit Ghorai was the lead author of the study.

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The modern world is filled with synthetic polymers, long-chained molecules designed by scientists to fill all manner of applications.

Researchers at FAMU-FSU College of Engineering have developed two closely related polymers that respond differently to high and low temperature thresholds, despite their similar design. The polymer pair could be used in applications in medicine, protein synthesis, protective coatings and other fields. Their work is published in Macromolecules.

“Typically, in order to have one thermal behavior, we have to prepare a polymer for that specific application, and if you want to have another extreme of polymer behavior, then you have to prepare a completely different polymer,” said coauthor Hoyong Chung, an associate professor in the FAMU-FSU College of Engineering. “But now, through this work, we have a single type of polymer that can be quickly adapted with minimal interference for both jobs.”

The researchers’ polymer is made with sulfoxide, a compound made of sulfur, oxygen and carbon molecules. One version contains an extra ingredient, a pair of hydrogen atoms known as a methylene group. This small structural variation is enough for each polymer to respond differently to variations in temperature.

Every mixture has critical temperatures above or below which the components will completely dissolve into a solution, regardless of the concentration of the various components in the mixture.

One version of the researchers’ polymer is soluble in water at low temperatures but becomes insoluble at higher temperatures. The other version displays the opposite behavior. It is insoluble at lower temperatures but dissolves when temperatures rise above a critical point.

“This contrasting behavior, which appeared with just a single minor change, was a surprising finding,” said postdoctoral researcher Biswajit Saha, the paper’s lead author. “It’s an exciting avenue for future research.”

Along with their development of this new, temperature-controllable polymer, the research team made other discoveries:

A new mechanism that governs a critical temperature threshold: Previous research showed that hydrogen atom bonds determined the temperature above which temperature-sensitive polymers dissolved in a solution, the so-called upper critical solution threshold. But Chung’s group found that the attraction between positively and negatively charged poles of different molecules — a process known as dipole-dipole interaction — also predicted the temperature at which their polymer would mix in water. Notably, his group has experimentally proved the presence of this interaction as a driving force of the thermal behavior.

Two-stage thermal behavior: Most solutions experience a single-phase change when they pass their temperature threshold. But the polymer developed by Chung’s team goes through phase changes in two stages. This feature could open potential new applications in medicine, such as a single medicine capsule that dissolves in the heat of a patient’s stomach in two stages, allowing for precise medicine delivery.

“We were fortunate to have these various insights with a single design,” Chung said. “A single polymer that can be ‘programmed’ to achieve different behaviors means this molecule can be easily adapted to different applications.”

This research was supported by the National Science Foundation.

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