US scientists create material for artificial photosynthesis to clean air

A new method for on-demand photosynthesis could not only give us cleaner air but produce energy at the same time, say scientists.

Researchers at the University of Central Florida have created a material that can absorb enough visible light to activate artificial photosynthesis, eliminating greenhouse gases and making fuel.

“The idea would be to set up stations that capture large amounts of carbon dioxide, like next to a power plant,” said Fernando Uribe-Romo, energy expert at the university and lead author of the study. “The gas would be sucked into the station, go through the process and recycle the greenhouse gases while producing energy that would be put back into the power plant.”

Scientists have previously attempted to tailor materials that absorb light for the chemical reaction – which involves carbon dioxide and sunlight converting into sugar – to take place.

However, they usually found that only ultraviolet light had enough energy to be picked up by everyday materials such as titanium dioxide.

But ultraviolet light only makes up 4% of the sunrays that reach Earth, according to the researchers. Only a few materials pick up visible light, which represents majority of the sun’s rays, and the ones that do – such as platinum – are too expensive.

Instead, Uribe-Romo’s team used a metal-organic framework (MOF) – a porous material made of metal ions in a hydrocarbon network. MOFs are often used to store gases such as hydrogen and carbon dioxide.

Similar to the way plants break down carbon dioxide, the researchers used the MOF to turn the gas into fuel. They added “light harvesting” molecules called N-alkyl-2-aminoterephthalates to titanium, and then manipulated the molecules to absorb the colour blue on the visible light spectrum.

The team then put the material inside a blue LED chamber together with carbon dioxide, and watched artificial photosynthesis take place while solar energy turned into chemical energy, cleaning the air.

But not everyone is so sure this technique can be implemented on a realistic scale, as “the vast majority of MOFs are far too expensive to produce,” said Timothy Easun, a materials scientist at Cardiff University, who was not involved in the research.

“They are also far too inefficient at carbon dioxide harvesting to ever be useful at scale in the capture and storage of the gas,” he added.

The Florida team is now working on tweaking the material to absorb other wavelengths of light, and suggest that the material could be used on house rooftops to clean the surrounding air and produce energy for the home.

The study has been published in the Journal of Materials Chemistry A.

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