This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Researchers at Kyushu University have developed a photocatalytic system that can selectively capture reacting molecules and hold them close to the active sites that absorb energy from light. This innovation addresses a long-standing challenge of having the photocatalyst maintain a high reaction rate even when the reacting molecules are present at very low concentrations.
Photocatalysis uses light to drive chemical reactions, reducing the need for high temperatures that may be necessary for other conventional catalytic reactions. These catalysts are specifically designed to absorb light and transfer its energy to the reactants. Since energy transfer depends on collisions between the excited photocatalyst and the reacting molecules, these collisions happen less frequently when the reacting molecules are dilute, leading to the reaction becoming slower and less efficient.
To address this limitation, a research team led by professor Takanori Iwasaki from Kyushu University's Faculty of Engineering, in collaboration with The University of Tokyo, developed an ionic photocatalytic system. Their study showcases how the counteranion, an often-neglected component of the photocatalyst, can be engineered to enhance reaction selectivity, efficiency and speed. The results were published in the journal Chemical Science on Oct. 8, 2026.
The team paired a light-absorbing ruthenium complex with their recently developed counteranion, BBcat. Counteranions are negatively charged ions that accompany positively charged ions in ionic chemical compounds. Although they can influence catalytic reactions, their role in photocatalysis has traditionally focused on their ability to donate electrons.
However, BBcat is unique in that it acts as a Lewis acid, meaning it can accept electron pairs. Thus, basic molecules are bound instead of being repelled by BBcat. In this way, the proposed system can capture specific reacting molecules and hold them near the light-absorbing component.
The proposed photocatalytic system increases the likelihood of energy transfer to the reacting molecules without requiring them to be present at high concentrations. The team tested the proposed photocatalyst in a reaction called [2+2] photocycloaddition, in which light helps two molecules form a four-membered carbon ring. The BBcat-based catalyst produced the desired product with a 76% yield.
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