Scientists achieve a major breakthrough in artificial photosynthesis

Photosynthesis is one of nature’s most efficient chemical processes, converting sunlight into energy with remarkable precision. Plants use this process to create sugar molecules and oxygen from water and carbon dioxide, sustaining life on Earth.

For decades, scientists have sought to mimic this natural mechanism, hoping to create artificial photosynthesis that could reduce atmospheric carbon dioxide and generate renewable energy. A new breakthrough has brought this vision closer to reality.

Natural photosynthesis relies on pigment-protein complexes that convert solar energy into electrochemical potential. Long-distance electron transfer (ET) minimizes charge recombination, ensuring long-lived charge-separated states and high quantum efficiencies. Researchers studying artificial photosynthesis have long aimed to replicate this energy conversion process.

Since the 1980s, scientists have worked to understand how electrons move between donor and acceptor molecules in synthetic systems. They have explored pathways that allow for efficient charge transfer, including those using π-conjugated spacers, DNA base pairs, and peptides.

Understanding the conditions under which charge moves most efficiently—whether through direct electron tunneling or stepwise hopping—has been a central challenge in the field.

A recent study led by chemist Frank Würthner from Julius-Maximilians-Universität (JMU) Würzburg, in collaboration with Professor Dongho Kim’s group at Yonsei University in South Korea, has made significant progress in this area.

Published in Nature Chemistry, their research introduces a new synthetic dye stack that closely mimics the structure of photosynthetic reaction centers in plants.

Using four perylene bisimide (PBI) molecules stacked in a precise arrangement, the researchers developed a system capable of absorbing light at one end, separating charge carriers, and transporting them step by step to the other end. This stacked structure efficiently moves energy in a manner similar to natural photosynthesis.

“We can specifically trigger the charge transport in this structure with light and have analyzed it in detail. It is efficient and fast. This is an important step towards the development of artificial photosynthesis,” said JMU PhD student Leander Ernst, who synthesized the stacked structure.

Perylene bisimide dyes have drawn attention due to their thermal and chemical stability, as well as their high absorption efficiency in the visible spectrum. Unlike conventional molecular dimers, these dyes can be arranged into aggregates that prevent energy loss, allowing for unique properties such as singlet fission and symmetry-breaking charge separation.

By engineering the molecular orientation of these stacks, researchers have achieved structures that avoid undesired exciton loss channels. This precise control over chromophore orientation ensures that energy remains efficiently transferred through the system.

For this study, Würthner’s team designed donor-bridge-acceptor (D–B–A) arrays with weak inter-PBI coupling. This setup reduces charge recombination and enables the formation of long-lived excitons, a crucial factor for harvesting solar energy.

In polar solvents, the system demonstrated efficient electron transfer, moving charges along the π-stacked PBI units with an attenuation factor (β) of just 0.2 Å−1. However, in non-polar solvents, the charge remained trapped, highlighting the importance of environmental conditions in optimizing charge transport.

The next step in the research is to expand these nanosystems beyond four stacked components, creating supramolecular wires that can transport energy over longer distances. If successful, these systems could be integrated into future solar energy technologies.

Artificial photosynthesis holds the potential to revolutionize energy production by generating clean fuel from sunlight. By mimicking the efficiency of nature’s energy conversion process, researchers are paving the way for sustainable energy solutions.

While challenges remain, this breakthrough marks a significant step toward harnessing the sun’s power to drive chemical reactions that could one day power industries, cities, and homes.

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