‘Flower-like’ catalyst mimics photosynthesis to turn CO2 into fuel with precision

Their research describes a ruthenium-based catalyst that uses light to trigger electron and proton transfers.

This reaction converts CO2 into formate (HCO2-), a compound used in fuels, pharmaceuticals, and antimicrobial applications.

Photosynthesis-inspired process

The researchers drew inspiration from nature’s own carbon conversion method—photosynthesis. “We are taking something cheap and abundant like CO2 and adding electrons and protons to convert it into something useful,” said Sai Puneet Desai, the paper’s lead author.

“In both our reaction and photosynthesis, the transfer of protons and electrons is promoted directly or indirectly by light,” Desai added. The team emphasized that their process, like photosynthesis, stores solar energy in chemical bonds. “You can think of it as storing light energy in the chemical bonds,” said co-author Andressa Müller.

Reshaping the catalytic approach

To increase the efficiency and stability of the reaction, the team modified how the catalyst interacts with CO2.

Traditionally, CO2 binds directly to the metal center in catalysts, which can cause side reactions and degrade the catalyst.

“Typically, in these types of CO2 conversions, you need to bind CO2 to a metal center on the catalyst,” said Javier Concepcion, who leads Brookhaven’s Artificial Photosynthesis group. “That means there are empty spaces for other competing molecules to come in and react with the metal.”

To avoid this issue, the team surrounded the metal center with ligands, which are chemical groups that act like petals around the metal “flower.”

“The catalyst is like a flower: The metal is the center of the flower and the petals are the ligands,” Müller explained. “We can tune the properties of the catalyst with these ligands, and all the chemistry takes place at one of the ligands instead of at the metal.”

Selective formate production

This ligand-based design shuts down unwanted reactions. “This mechanism is highly selective; only formate is produced,” said Concepcion. Competing products like hydrogen or carbon monoxide don’t form because they require direct metal interaction. “In this case, because the mechanism is ligand based, there is no chance for these other products to be generated,” he said.

Towards sustainable catalysis

Another major advantage of this approach is its flexibility. The central metal can be swapped as the ligands carry out the chemistry. “Since the chemistry happens on the ligands and not on the metal, this opens the possibility of using other metals at the core of the catalyst,” Müller said.

The current study used ruthenium, but the same strategy worked with iron, which is far more abundant and affordable. “This paper demonstrates that this ligand-based strategy is generalizable to other metals,” Concepcion noted. “Our goal is to move toward Earth-abundant metals. It doesn’t get more abundant than iron.”