Carbon capture breakthrough could lead to reversal of emissions

Handful of new porous material could absorb as much carbon dioxide as a tree does in a year

Scientist say they have developed a highly absorbent material that could revolutionise carbon capture technology. PA

Researchers may be putting humanity on the path to negative carbon emissions after the discovery of a type of highly porous material which can capture and store carbon dioxide more efficiently than ever before.

Carbon capture has become a promising tool in the fight against climate change by lowering atmospheric greenhouse gases and CO2 levels, which are 50 per cent higher than they were a century ago. The Intergovernmental Panel on Climate Change has stressed the importance of carbon capture, saying humanity will not reach its goal of limiting global warming to 1.5°C without it.

However, the current technology only works on highly concentrated sources of carbon, such as those from power plant exhausts and other industrial output, rather than the "ambient" air that we typically breathe.

Chemists at the University of California, Berkeley say they have developed a highly absorbent material which can pull carbon from the air without degradation by water or other contaminants, which is one of the limitations of existing direct air-capture technology. In a new study, published in Nature, researchers outlined how a covalent organic framework (COF) material, described as a kind of ultra-porous organic crystals, can clean ambient air in the environment through direct air capture.

The new porous COF efficiently binds with CO2 molecules (blue and orange balls) found in ambient air. Photo: Chaoyang Zhao for UC Berkeley

"Direct air capture is like a giant vacuum cleaner that removes CO2 out of the air, captures it, and stores", the study's first author Zihui Zhou told The National. "It helps reduce the overall amount of CO2 in the atmosphere, which is key for tackling climate change".

The COF material builds on previous research developed by Omar Yaghi, a professor of chemistry at UC Berkeley and co-author of the study. His team have spent the last 20 years developing COFs that have a strong enough backbone to withstand contaminants that break it down over repeated cycles.

"I am excited about it because there's nothing like it out there in terms of performance. It breaks new ground in our efforts to address the climate problem," he said.

The Berkeley researchers put a powder of COF in a tube and pushed it through regular outdoor air to see how it would perform. The team were excited to find the carbon concentration dropped to zero, indicating that the material had completely cleaned the air of CO2.

They were further encouraged when it demonstrated excellent stability, maintaining its performance after 100 cycles over 20 days. Ms Zhou said that a mere 200g of the material can take up to 20kg of CO2 in a year, about the same as a tree. Such a discovery could even lead to negative emissions, allowing humanity to reverse some of the damage done by industrial pollutants that have been pumped into the air since the Industrial Revolution.

"Direct air capture is a method to take us back to like it was 100 or more years ago," Ms Zhou said. "Currently, the CO2 concentration in the atmosphere is more than 420 parts per million (ppm), but that will increase to maybe 500 or 550 before we fully develop and employ flue gas capture. So if we want to decrease the concentration and go back to maybe 400 or 300 ppm, we have to use direct air capture."

Prof Yaghi believes the new material could be substituted easily into carbon capture systems already deployed or being piloted to remove CO2 from refinery emissions and capture atmospheric CO2 for storage underground.

"This COF has a strong chemically and thermally stable backbone, it requires less energy, and we have shown it can withstand 100 cycles with no loss of capacity. No other material has been shown to perform like that," Prof Yaghi said. "It's basically the best material out there for direct air capture."

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