Phenol is an organic compound that is considered a “platform molecule.” These molecules come from sustainable organic matter and can be used as a building block for other chemical compounds. Because phenol has high oxygen content and is too stable, it hasn’t been used to develop fuel. By adding hydrogen through a process called hydrogenation, phenol can be converted to cyclohexanone or cyclohexanol.
Researchers searching for more efficient catalytic systems to select for cyclohexanone through phenol hydrogenation propose using palladium-polyoxometalates cluster catalysts. The results were published in Polyoxometalates on 30 January.
“Phenol stands out as a versatile platform molecule for its structural diversity and abundance. However, its high oxygen content and intrinsic stability hinder direct fuel applications. The selective hydrogenation of phenol to cyclohexanone or cyclohexanol is a practical alternative, affording intermediates of considerable industrial relevance. Notably, cyclohexanone serves as a widely used solvent in coatings, adhesives, and resins,” said Zhongling Lang, a professor at Northeast Normal University in Changchun, China.
To test for selective phenol hydrogenation reactions, the reaction was tested in an autoclave machine, which is a machine that uses temperature and pressure to initiate processes. Palladium-polyoxometalates clusters were synthesized using this method. Polyoxometalates clusters help guide the formation of the catalysts because they have an oxygen-rich surface and high negative charges. This forms the palladium clusters that are stabilized by the polyoxometalates.
These newly formed catalysts are smaller and have a smaller structure. The best catalyst was a palladium-polyoxometalates cluster called Pd-PMo 10 V 2, which had the best catalytic performance. The researchers found that without Pd-PMo 10 V 2 , the palladium nanoparticles are irregular. “These results confirm that Pd-PMo 10 V 2 functions as templates or multi-dentate ligands to form such cluster catalysts. In addition, the synthesis temperature and OAm/OA ratio considerably affect the regular arrangement of the cluster catalysts. An increase in teamperature or OAm proportion accelerates the nucleation and growth of Pd species, which hinders the formation of well-defined cluster catalysts,” said Lang.
Pd-PMo 10 V 2 also has a very uniform and homogenous composition, since the oxygen, phosophorous, vanadium, molybdenum and palladium are evenly distributed. The study also looked at the crystal structure and chemical composition of Pd-PMo 10 V 2. Researchers determined that while phenol conversion increased as temperature increased, the higher temperatures also resulted in over-hydrogenation. This means the researchers would end up with cyclohexanol instead of cyclohexanone. They found that 60 degrees Celsius is the optimal temperature to select for cyclohexanone.
By testing combinations of palladium clusters and up to 5 polyoxometalate cluster catalysts, Pd-PMo 10 V 2 was found to be the best catalyst in the selective hydrogenation of phenol to cyclohexanone. When Pd-PMo 10 V 2 is used, it reached a phenol conversion of 99.9% resulting in cyclohexanone 95.4% of the time. It also maintained structural integrity and catalytic stability through six cycles. This catalyst works so well because of how the polyoxometalates clusters and palladium work together. The polyoxometalates clusters stabilize the palladium clusters and function as electron/hydrogen acceptors through the spillover effect. Hydrogen spillover is when hydrogen atoms move from a metal catalyst to nonmetal. At the same time, the small palladium clusters are sites for H 2 activation and dissociation.
Looking ahead, researchers hope to test practical uses for this catalyst. “This work offers a promising strategy for the rational design of noble-metal cluster-based catalysts with enhanced activity and selectivity, paving the way for advanced applications in selective hydrogenation reactions,” said Lang.
Other contributors include Yanchun Liu, Zixuan Liu, Ruiqi Yao, Feiyang Yu, Aicen Li, and Huaqiao Tan of Northeast Normal University.
The National Natural Science Foundation of China, the National Science Foundation of Jilin Province Science and Technology Department, and the Postdoctoral Fellowship Program of CPSF supported this research.
D OI Link:
https://doi.org/10.26599/POM.2026.9140109
About Polyoxometalates
Polyoxometalates (ISSN 2957-9821) is a peer-reviewed (single-blind), open-access and interdisciplinary journal, sponsored by Tsinghua University. Polyoxometalates publishes original high-quality research papers and significant review articles that focus on cutting-edge advancements in Polyoxometalates, and clusters of metals, metal oxides and chalcogenides. Rapid review to ensure quick publication is a key feature of Polyoxometalates . The journal is indexed by ESCI (IF 2025 = 10.4, Top 3), Scopus (CiteScore 2025 = 17.6, Top 3), Ei Compendex, CAS, and DOAJ. For details about Polyoxometalates , please visit: https://www.sciopen.com/journal/2957-9821 .
Polyoxometalates
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