Every day, without effort, plants do something chemists have spent decades trying to copy: they catch sunlight and lock its energy into chemical bonds. Replicating that trick in a lab — well enough to actually power the world — has proven far harder than it looks.
Now a team at the University of Basel says it has cleared a meaningful hurdle. In a study published in Nature Chemistry, Professor Oliver Wenger and doctoral student Mathis Brändlin describe a new five-part molecule designed to mimic the core logic of photosynthesis. What it can do with light, and why that matters for solar fuels, is where the story gets interesting.
A blueprint borrowed from leaves
Plants have been running the same solar-powered chemistry for billions of years. Sunlight hits a leaf, and a cascade of reactions converts CO2 into energy-rich sugar molecules. Animals and humans then burn those carbohydrates, releasing the CO2 back into the air — a closed loop with no net carbon added.
Artificial photosynthesis aims to copy that loop, but instead of making sugar, the goal is to produce solar fuels: hydrogen, methanol, synthetic petrol. Burning these fuels releases only as much CO2 as was absorbed to make them, so they qualify as carbon-neutral. The climate math works out.
The central obstacle is charge accumulation. Driving useful chemistry — splitting water into hydrogen and oxygen, for example — requires storing multiple electric charges simultaneously. Generating one charge with light is manageable. Holding four at once, without them collapsing back, is where most attempts have stalled.
How the new molecule is built
The Basel team’s solution is a molecule assembled from five distinct parts, connected in a linear chain. Each segment has a specific job, and together they function like a miniature assembly line for moving and storing electric charge.
At one end sit two donor units. When excited, they release electrons and become positively charged. At the opposite end, two acceptor units capture those electrons and go negative. The symmetry is deliberate — positive charges accumulate on one side, negative on the other. A central light-absorbing component bridges the two halves, triggering the electron transfer and sending charges racing toward the outer ends.
Two flashes, four charges
The molecule reaches its fully charged state in two steps. The first flash of light hits the central absorber, generating one positive and one negative charge. Those charges separate and migrate outward to opposite ends of the molecule. A second flash repeats the process, leaving the molecule holding two positive charges on the donor side and two negative on the acceptor side — four stored charges in total.
Four charges are enough to drive reactions like splitting water into hydrogen and oxygen, a key step in producing solar fuel. Crucially, the charges remain stable long enough to participate in further chemical reactions, rather than recombining and dissipating as heat — which has been the undoing of many earlier designs.
Why dim light is a big deal
Earlier work on multi-charge storage required intense laser light — conditions that bear little resemblance to a rooftop solar panel or a sun-drenched field. That gap between lab conditions and real-world sunlight has been one of the field’s persistent problems.
The stepwise approach changes that dynamic. “This stepwise excitation makes it possible to use significantly dimmer light,” Brändlin explained. “As a result, we are already moving close to the intensity of sunlight.” That shift toward something resembling natural light is a meaningful practical step, not merely a laboratory refinement.
The team is careful not to overclaim. The molecule does not yet constitute a working artificial photosynthesis system. “But we have identified and implemented an important piece of the puzzle,” Wenger noted. Progress in this field tends to arrive in increments, and this is one of them.
What comes next for solar fuels
Several challenges remain before artificial photosynthesis can produce usable fuel at any meaningful scale. The stored charges still need to be connected to catalysts that can complete the chemical reactions — converting electrons and protons into hydrogen, for instance, rather than simply holding them in place. That coupling work is where much of the next research effort will likely go.
Wenger framed the findings as a contribution to foundational science, arguing that the results deepen understanding of the electron transfers at the heart of the field. That mechanistic knowledge tends to shape the next generation of molecular designs.
The broader landscape of sustainable energy research is moving quickly, and solar fuels remain one of its more ambitious targets. The Basel work suggests that light requirements for multi-charge storage are not as prohibitive as once thought. “We hope that this will help us contribute to new prospects for a sustainable energy future,” Wenger said. Whether this particular molecule becomes part of a working system, or simply points the way toward one, the next experiments will be worth watching.
Carlos is an engineer with strong expertise in technical and industrial topics. He previously worked at international companies such as Siemens and speaks Spanish, German, English, and Italian.
