Sulfones, a class of sulfur-containing compounds, are chemically derived from the selective oxidation of sulfides. While these compounds form the core of the pharmaceuticals, solvents and polymer industries, their chemical synthesis is often hindered by high reaction temperatures and extreme reaction conditions. Additionally, these also require costly additives and harsh solvents for production. Against this backdrop, a team of researchers from Japan introduced a new catalyst design, capable of overcoming the limitations of conventional synthesis, offering higher selectivity and a better yield for sulfones.
The research team, led by Professor Keigo Kamata from Institute of Science Tokyo, Japan, utilized advanced catalyst synthesis techniques to explore how variations in elemental composition and crystal structure contribute to catalytic performance for sulfide oxidation at a lower temperature. Their findings were published online in Advanced Functional Materials on April 03, 2025.
"Sulfide oxidation using molecular oxygen as the oxidant is one of the most challenging reactions in organic chemistry, and the development of new solid catalysts that can facilitate this type of reaction has gained considerable attention in recent years," notes Kamata.
Addressing this demand, the researchers focused on perovskite oxide, a material widely used for catalysis. To enhance the reactivity of a specific metal-oxygen species (face-shared oxygen) in a hexagonal perovskite based on strontium (Sr), manganese (Mn) and oxygen (O) called SrMnO₃, they introduced ruthenium (Ru) atoms in place of some of the Mn atoms. This subtle modification created oxygen vacancies inside the crystal, which significantly improved the catalyst's ability to transfer oxygen atoms—an essential step in sulfide oxidation.
The result was an efficient catalyst known as SrMn₁₋ₓRuₓO₃, which was capable of converting sulfides to sulfones with an unprecedented selectivity of 99% at a reaction temperature as low as 30°C. This was a dramatic shift from that of conventional systems, which typically require 80–150°C for the same reaction.
Conventional reaction systems rely on large amounts of precious metals for selectivity. While the researchers did utilize Ru, they achieved greater selectivity at just 1% Ru doping, which significantly cuts down the use of precious metals. Using mechanistic studies, the researchers further uncovered the mechanism behind the remarkable catalytic performance.
"The catalysis follows a Mars–van Krevelen mechanism, in which the oxygen atoms on the crystal surface transfer to the sulfides, leaving behind oxygen vacancies. These vacancies are then filled by molecular oxygen in the atmosphere, and the cycle continues," explains Kamata.
Another striking advantage of the developed catalyst was its durability. The team confirmed that the catalyst could be reused at least five times without any significant loss of performance. Moreover, the system was applicable to a wide range of sulfide substrates, which included aromatic, aliphatic, making it highly versatile for industries.
While the present study focused only on sulfide oxidation, the implications of this work could extend to a wide range of oxidation reactions, transforming environmental cleanup and energy conversions. The team hopes that their findings will inspire new catalyst designs that offer greater sustainability and cost-efficiency. The research also underscores the synergistic effect of multiple elements in creating sustainable materials, paving the way for greener and smarter industrial chemistry.
