Everyone’s talking about carbon capture and storage (CCS) given the need to reduce atmospheric greenhouse gases. The planet’s future rests on humanity’s ability to slow down global warming.
Unfortunately, current carbon capture methods are not efficient.
They work decently for concentrated sources of carbon such as power plant exhaust, but fall short in ambient air where carbon dioxide concentrations are lower.
It’s in this context that direct air capture (DAC) comes into the picture. It’s the solution that could reverse the escalation of CO2 levels.
With current CO2 levels reaching 426 parts per million (ppm) — a full 50% higher than pre-Industrial Revolution levels — the world needs DAC.
Without it, limiting global warming to 1.5 °C (2.7 °F) above pre-global averages, as per the Intergovernmental Panel on Climate Change’s recommendations, seems like a far-off goal.
A team of chemists from the University of California, Berkeley developed an absorbing material that might make the goal of negative emissions and carbon capture a reality.
Covalent organic framework (COF) captures CO2 from ambient air with no degradation caused by water or other contaminants, surpassing the limits of current DAC technologies.
“We took a powder of this material, put it in a tube, and we passed Berkeley air — just outdoor air — into the material to see how it would perform, and it was beautiful. It cleaned the air entirely of CO2. Everything,” said Omar Yaghi, the James and Neeltje Tretter Professor of Chemistry at UC Berkeley and the senior author of the paper.
What makes this development more promising is its versatility.
The material could adapt to existing carbon capture systems or remove CO2 from refinery emissions and capture atmospheric CO2 for underground storage.
The material’s efficacy is such that 200 grams absorbs as much CO2 in a year (around 20 kilograms or 44 pounds) as a tree.
Efforts to tackle climate change focus largely on slowing down the release of CO2 into the atmosphere.
“Flue gas capture is a way to slow down climate change because you are trying not to release CO2 to the air. Direct air capture is a method to take us back to like it was 100 or more years ago,” explains the principal author of the study, UC Berkeley graduate student Zihui Zhou.
“Currently, the CO2 concentration in the atmosphere is more than 420 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.”
One of the things that makes this material stand out is it’s made of covalent carbon-carbon and carbon-nitrogen double bonds, some of the strongest chemical bonds in nature.
Scientists designed the material, COF-999, to withstand a range of contaminants including acids, bases, water, sulfur, and nitrogen.
It turns out that 400 ppm CO2 air when pumped through the COF at room temperature (25 °C) and 50% humidity reaches half its capacity in 18 minutes and fills in about two hours. If optimized, scientists could reduce it to a fraction of a minute.
The COF takes in up to 2 millimoles of CO2 per gram, outperforming other solid sorbents. After 100 cycles, there was no loss of capacity.
“It’s basically the best material out there for direct air capture,” Yaghi said.
Scientists are excited about blending artificial intelligence with the type of chemistry the team works on.
AI can speed up the design of even better COFs and MOFs for carbon capture by identifying the chemical conditions required to synthesize their crystalline structures.
Such a blend of AI and chemistry could make the world’s goal of negative emissions a reality and bring humanity closer to a healthier, more sustainable world.
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