Mimicking photosynthesis to produce fuel

RESEARCHERS at the Bengaluru- based Jawaharlal Nehru Centre for Advanced Scientific Research (JNCASR) may have designed an artificial system that mimics how plants and other photosynthetic organisms use sunlight to convert atmospheric carbon dioxide and water into molecules that can be used as fuel.
Still in an early stage of development, the artificial photosynthetic system developed by a team led by JNCASR professor Tapas Kumar Maji can capture CO₂ from the atmosphere and convert it into carbon monoxide which can be used as fuel in internal combustion engines.

Typically such systems, as in plants, work through two linked chemical reactions: one that splits water into protons and oxygen gas, and another that converts CO₂ into CO. CO can then be converted into hydrocarbon fuels through an established industrial process called Fischer-Tropsch synthesis.

If carried out at commercial scale, such technology interventions can help solve two intractable problems faced by humankind. Once such technologies are perfected, they can help sequester carbon dioxide emitted into the atmosphere due to industries and fossil fuel use and thus reduce problems precipitated by climate change. Second, they can yield greener ways to produce fuels. But they still have a long way to go before they become economically viable.

The system was reported in a paper published in Energy and Environmental Science journal in early March. The integrated catalytic system that they developed is based on a metal-organic framework (MOF-808) comprising of a photosensitiser (a class of molecules that absorb light and transfer electrons from the incident lightcto nearby molecules) and a catalytic centre that can eventually reduce CO₂ to CO.

To do this, the scientists kept the photosensitiser, a chemical called ruthenium bipyridyl complex, and the catalyst, another chemical called rhenium carbonyl complex, closer to each other inside the nanospace of MOF-808. When both these molecular entities stay in close proximity in the confined space the porous MOF-80,cthere could be an excellent uptake of CO₂ at room temperature.

According to the scientists, the catalyst showed excellent ability to reduce CO₂ to CO. It also split water to produce oxygen. They also found that as the integrated catalytic assembly does not participate directly in chemical reaction, it can be reused for several cycles without any loss in its activity.

The JNCASR team believes this intricate design and approach will pave the way to develop new integrated catalytic systems to capture CO₂ and convert it into different energy-rich chemical feedstocks by mimicking
photosynthesis.