In a major breakthrough for carbon capture technology, chemists at the University of California, Berkeley, have engineered a new material capable of capturing carbon dioxide (CO2) from industrial exhaust gases at unprecedentedly high temperatures. This innovation could change the way we approach dealing with some of the most carbon-intensive industries-historically, among the toughest to clean up-making cement and steel production easier in line with carbon-reducing goals. Since it is a type of metal-organic framework known as ZnH-MFU-4l, the novel material can conceivably handle high temperatures up to 300°C, which are common in exhaust gases in both industries.
The need for new carbon capture technology has hastened lately because of the recognition of industrial emissions’ role in creating and triggering climate change. Industry sectors such as cement, steel-making, and others that involve the use of fossil fuels in high-temperature processes have especially been hard to decarbonize even as sources such as renewable energy cut down the reliance on CO2-emitting, fossil fuel-burning power plants. The development of such a material may finally be a solution to one of the most persistent challenges with sustainability and climate action: capturing CO2 from these hot exhaust gases.
Current capture technologies rely on liquid amines to absorb CO2. However, such an amine-based system operates effectively between 40°C and 60°C and therefore is not applicable to the high temperature of exhaust gases from cement and steel plants. For example, in some cases, exhaust gases can rise above 200°C, and industrial processes can sometimes even get as high as 500°C. It costs too much to cool gas streams down to temperatures at which amines can work, making these existing systems unviable. This has limited carbon capture technologies in many industrial applications.
The UC Berkeley research team discovered a breakthrough away from traditional amine-based carbon capture systems that introduces a new mechanism of CO2 capture with MOFs. These frameworks hold metal ions connected by organic linkers, renowned for their large surface areas and porous structures, which make them very effective as gas adsorbers. The ZnH-MFU-4l MOF developed by the research team has zinc hydride sites within the pores that are capable of binding CO2 molecules at significantly higher temperatures than the materials currently in use. This leads to effective capture of the carbon dioxide from a hot industrial exhaust system without cooling the hot industrial exhaust.
The ZnH-MFU-4l MOF could capture CO2 at the concentration typical of emissions of cement and steel factories, that are around 20% to 30% of CO2, as well as from natural gas power plants with a lower CO2 level of approximately 4%. The MOF could capture up to 90% of the CO2 it encountered in laboratory tests simulating industrial conditions, a performance level critical for large-scale efforts to capture CO2 from industrial emissions. Once captured, the CO2 can be released by reducing the partial pressure of CO2, either by flushing the MOF with a different gas or by applying a vacuum. This process makes the material reusable for multiple CO2 capture cycles, further enhancing its efficiency.
One of the most striking aspects of this discovery is that it challenges previous assumptions about the feasibility of capturing CO2 at temperatures above 200°C. Such porous materials as MOFs have long been believed not to be capable of capturing gases at such high temperatures because the temperature increases would favor gas molecules to evolve into a free and unbound state. In contrast, work by the UC Berkeley team indicates that by using the right chemical functionality—the zinc hydride sites on this MOF—the material can pull in CO2 fast and then easily release it, even at temperatures as high as 300°C.
The breakthrough also serves as a departure from work previously focused primarily on amine-based adsorbents. Indeed, amines were mostly targeted by the scientists for so many years regarding the research on CO2 capturing. However, they lose effectiveness at high temperatures. On the other hand, metal hydride sites with higher stability at elevated temperatures allow the ZnH-MFU-4l MOF to capture CO2 more effectively in harsh industrial environments. This stability also makes it a promising alternative for industries that have, until now, been unable to adopt carbon capture technologies due to the extreme conditions related to their processes.
Researcher Kurtis Carsch, a postdoctoral fellow at UC Berkeley, and graduate student Rachel Rohde are further investigating the possibility for the ZnH-MFU-4l MOF in other gas separation applications. This research has opened up new possibilities with regard to functional adsorbent design that may operate efficiently under high temperatures, a critical factor in the industrial and environmental processes involving it. They are also exploring ways to modify the material to further enhance CO2 adsorption capacity.
Jeffrey Long, a professor of chemistry at UC Berkeley and the senior author of the study, has been conducting research on CO2-adsorbing MOFs for over a decade. His previous work led to the development of a promising MOF material that was later commercialized by his startup, Mosaic Materials, and eventually acquired by Baker Hughes. This new study expands on that prior work and is an important advancement toward more efficient, high-temperature CO2 capture technologies.
The discovery of ZnH-MFU-4l is an intellectual feat, but it might also make a difference in affecting change across the globe in the battle against climate change. With the continued attempts of industries to reduce their carbon footprints, the development of materials like this MOF could have a significant role in mitigating the effects of industrial emissions. Thus, by providing a low-cost and energy-efficient way of capturing CO2 from high-temperature exhaust streams, this breakthrough could help pave the way for more sustainable industrial practices and contribute to the global transition toward a low-carbon future.