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UC Berkeley researchers developed COF-999, a porous material that captured carbon dioxide from outdoor air in laboratory tests. It took up CO₂ at roughly 400 parts per million and could be regenerated at about 60°C. That makes it a promising advance in direct air capture—not evidence that the material can yet reverse rising atmospheric CO₂. The climate impact depends on building practical systems, powering them cleanly, and permanently storing the captured carbon.
What is COF-999?
COF-999 is a covalent organic framework (COF): a porous, crystalline structure made from organic molecules connected by covalent bonds. Researchers modified its pores with polyamine groups. Those amines interact with CO₂, allowing the material to adsorb the gas as air passes through it. Adsorption means the CO₂ is held on or within the material; it is not permanently converted into another substance.
The term “molecular sponge” is a metaphor for the material’s porous structure. COF-999 is a sorbent intended for use in capture equipment, not a ready-made air filter or consumer device. The original study appeared in Nature in 2024.
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Point-source capture targets exhaust from facilities such as cement plants or power stations, where CO₂ is much more concentrated than it is in ordinary air. Direct air capture (DAC) must isolate CO₂ from ambient air, where it is present at only hundreds of parts per million. That means equipment must process large volumes of air while contending with water vapor, oxygen, nitrogen, weather, and possible contaminants.
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COF-999 matters because the researchers tested it against outdoor air rather than relying only on a concentrated industrial exhaust stream. Its performance in a Berkeley test, however, does not establish how it would work in every climate or in a full-scale plant.
What the COF-999 experiments measured
| Measure | Reported result |
|---|---|
| CO₂ concentration | Approximately 400 ppm |
| Capacity in dry conditions | 0.96 mmol of CO₂ per gram |
| Capacity at 50% relative humidity | 2.05 mmol of CO₂ per gram |
| Time to reach half of capacity | 18.8 minutes |
| Regeneration temperature | Approximately 60°C under the reported experimental conditions |
| Outdoor testing | Berkeley, California |
| Adsorption–desorption cycling | More than 100 tested cycles, with performance retained in the reported test |
These figures describe different properties. Capacity measures how much CO₂ a given mass of material takes up; the half-capacity time describes uptake speed in the test; regeneration temperature describes one condition used to release CO₂. None alone establishes a system’s cost, total energy demand, or useful operating life.
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How the material captures and releases CO₂
- Air is brought into contact with the porous material.
- CO₂ diffuses into the framework’s channels, where amine groups retain it preferentially.
- Once the sorbent has captured CO₂, it is heated under the study’s regeneration conditions—about 60°C—to release the gas for collection.
- The regenerated material can be returned to the capture step.
A regeneration temperature near 60°C is encouraging because it points to relatively low-temperature heat. It does not mean the process is energy-free: a working system also has to move air, heat equipment and potentially moisture, handle the released gas, and prepare it for transport or storage.
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Why the humidity result is notable—and limited
At approximately 400 ppm CO₂, the study reported a higher capacity at 50% relative humidity than in dry conditions. That is a notable result for a material tested for air capture, since moisture can complicate the performance of some sorbents. It does not show that every level of humidity helps: the reported measurements do not establish performance across all climates, rainfall patterns, contaminants, or long-duration exposure.
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What the “200 grams per year” comparison means
A University of California public explanation estimated that 200 grams of COF-999 could capture about 20 kilograms of CO₂ per year, and compared that amount with a tree. Treat this as an illustrative estimate, not a measured output from a commercial plant. It depends on operating conditions and repeated capture and regeneration; it does not mean that 200 grams of material alone can remove that amount permanently without equipment, energy, and a route to storage.
Could COF-999 reverse rising CO₂ levels?
Not by itself, and the study did not demonstrate that outcome. A material capturing CO₂ is only one part of atmospheric removal. The captured gas must be kept out of the atmosphere, and the full process must avoid emitting so much greenhouse gas that it cancels the benefit.
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- Capture: COF-999 can take up CO₂ from air under the tested conditions.
- Removal: The captured CO₂ needs a durable destination. If it is made into a product that later releases the gas, the result may be temporary use rather than permanent removal.
- Climate benefit: Energy, material production, air handling, compression, transport, and storage all affect net emissions. Permanent geological or mineral storage would also need suitable infrastructure and monitoring.
For atmospheric levels to fall, removal would have to exceed ongoing emissions over time. A successful sorbent could contribute to that effort, but COF-999 has not been shown to do so at climate scale. Directly reducing emissions remains essential.
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The Nature study establishes material performance in its reported experiments; it does not establish the economics or lifecycle results of a complete DAC plant. Moving from a promising powder to a dependable system requires more than repeating the laboratory test.
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- Scale and manufacturing: Whether the material can be produced in large quantities at acceptable cost, with raw materials available at the needed scale.
- Practical contactors: Whether it can be shaped into robust pellets, coatings, monoliths, or another form that exposes it to air without excessive resistance or dust.
- Energy and operations: The electricity and heat needed for fans, regeneration, moisture management, and CO₂ compression in a complete system.
- Long-term performance: Operation over years and far more than 100 cycles, including exposure to dust, ozone, sulfur and nitrogen compounds, and other atmospheric contaminants.
- Net removal and storage: A lifecycle assessment, a cost per tonne of net CO₂ removed, and a durable, monitored destination for the captured gas.
- End of life: Safe handling or disposal if the sorbent degrades or becomes contaminated.
These are central design questions because DAC has to move a great deal of dilute air. Fan power, contactor design, heat supply, and the treatment of the released CO₂ can determine whether a good sorbent becomes a useful system.
How it fits among other carbon-capture approaches
There is no single performance measure that establishes which capture approach is best. COF-999’s reported results are promising under the tested conditions, but they do not prove superiority in cost, lifecycle emissions, durability, or plant performance.
| Approach | How it differs | Trade-off to consider |
|---|---|---|
| Liquid amines | Use a liquid chemical solution to absorb CO₂. | Established chemistry and familiar engineering, but regeneration can require substantial heat; solvent degradation and corrosion can also matter. |
| Solid amine sorbents | Hold amine chemistry on solid materials for use in contactors. | May support modular equipment and lower-temperature regeneration, but durability and humidity response vary by material. |
| Metal-organic frameworks | Use porous materials whose structures can be tuned for gas capture. | Performance, stability, manufacturing cost, and scale-up depend on the specific chemistry. |
| Alkaline mineralization | Uses alkaline materials or minerals to bind CO₂ in mineral forms. | Can offer durable storage, but may involve large material flows and processing requirements. |
| Moisture-driven or electrochemical DAC | Uses moisture changes or electrochemical processes as part of capture or regeneration. | May offer alternatives to thermal regeneration, but many approaches remain at research or pilot stage. |
Research continues beyond COF-999. In February 2026, Berkeley reported COF-1000 as a newer material that captures CO₂ from outdoor air faster than previously reported materials. That development places COF-999 in an evolving research program rather than identifying it as the group’s final or latest solution. Berkeley’s COF-1000 announcement describes that later work.
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What the breakthrough does—and does not—show
COF-999 is a meaningful materials advance: the researchers demonstrated outdoor-air capture, reported useful capacity under humid conditions, and regenerated the material at about 60°C. The results support further development and system testing. They do not establish commercial availability, a cost per tonne, net-negative emissions, or a way to reverse atmospheric CO₂ growth today. That would require an integrated, affordable system running on low-carbon energy and paired with durable storage at a vastly larger scale.
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