Researchers at the University of Cambridge (UK) have developed a reactor that pulls carbon dioxide directly from the air and converts it into sustainable fuel, using sunlight as the power source. The researchers say their solar-powered reactor could be used to make fuel to power cars and planes, or many chemicals and pharmaceuticals products. It could also be used to generate fuel in remote or off-grid locations.

The results are reported in an open-access paper in the journal Nature Energy.

Direct air capture is an emerging technology to decrease atmospheric CO₂ levels, but it is currently costly and the long-term consequences of CO₂ storage are uncertain. An alternative approach is to utilize atmospheric CO₂ on-site to produce value-added renewable fuels, but current CO₂ utilization technologies predominantly require a concentrated CO₂ feed or high temperature.

Here we report a gas-phase dual-bed direct air carbon capture and utilization flow reactor that produces syngas (CO + H2) through on-site utilization of air-captured CO₂ using light without requiring high temperature or pressure. The reactor consists of a bed of solid silica-amine adsorbent to capture aerobic CO₂ and produce CO₂-free air; concentrated light is used to release the captured CO₂ and convert it to syngas over a bed of a silica/alumina-titania-cobalt bis(terpyridine) molecular–semiconductor photocatalyst.

We use the oxidation of depolymerized poly(ethylene terephthalate) plastics as the counter-reaction. We envision this technology to operate in a diurnal fashion where CO₂ is captured during night-time and converted to syngas under concentrated sunlight during the day.

—Kar et al.

Carbon Capture and Storage (CCS) has been touted as a possible solution to the climate crisis, and has recently received £22 billion in funding from the UK government. However, CCS is energy-intensive and there are concerns about the long-term safety of storing pressurized CO₂ deep underground, although safety studies are currently being carried out.

Professor Erwin Reisner’ team’s newest system takes CO₂ directly from the air (DAC) and converts it into syngas: a key intermediate in the production of many chemicals and pharmaceuticals. The researchers say their approach, which does not require any transportation or storage, is much easier to scale-up than earlier solar-powered devices.

The device, a solar-powered flow reactor, uses specialized filters to grab CO₂ from the air at night, like how a sponge soaks up water. When the sun comes out, the sunlight heats up the captured CO₂, absorbing infrared radiation and a semiconductor powder absorbs the ultraviolet radiation to start a chemical reaction that converts the captured CO₂ into solar syngas. A mirror on the reactor concentrates the sunlight, making the process more efficient.

a, Schematics of the system during light-off night operation. b, Schematics of the overall system during light-on day operation. c, The carbon capture unit with chemical CO₂ capture and release equations. d, The solar-driven CO₂U unit material composition and the relevant reduction and oxidation reactions. RT, room temperature; MFC, mass flow controller; PEI, polyethyleneimine; PET, poly(ethylene terephthalate); EG, ethylene glycol. Kar et al.

The researchers are currently working on converting the solar syngas into liquid fuels, which could be used to power cars, planes and more.

The researchers say that a particularly promising opportunity is in the chemical and pharmaceutical sector, where syngas can be converted into many of the products we rely on every day, without contributing to climate change. They are building a larger scale version of the reactor and hope to begin tests in the spring.

If scaled up, the researchers say their reactor could be used in a decentralized way, so that individuals could theoretically generate their own fuel, which would be useful in remote or off-grid locations.

The technology is being commercialized with the support of Cambridge Enterprise, the University’s commercialisation arm. The research was supported in part by UK Research and Innovation (UKRI), the European Research Council, the Royal Academy of Engineering, and the Cambridge Trust. Erwin Reisner is a Fellow of St John’s College, Cambridge.

Resources

• Sayan Kar et al. Direct air capture of CO₂ for solar fuels production in flow. Nature Energy (2025) doi: 10.1038/s41560-025-01714-y