
Prof. Veronique Van Speybroeck’s research group, embedded in the Center for Molecular Modeling, in collaboration with the groups of Prof. Bert Sels (Center for Sustainable Catalysis and Engineering, KU Leuven) and Prof. Bert Maes (Organic Synthesis Division, Department of Chemistry, University of Antwerp), has provided new insights into the complex behavior of acid catalysis in nanoconfined environments.
Aqueous acid catalysis involves the acceleration of chemical reactions in the presence of solvated protons, typically existing as hydronium ions (H3O+). In bulk liquid water, these hydronium ions are fully solvated, meaning they are surrounded and stabilized by water molecules. This is the case, for example, in a glass of lemon juice, which contains citric acid. However, acid catalysis can also occur in solid acid catalysts like zeolites. Zeolites can be thought of as sponges with pores just large enough to accommodate small molecules. When hydronium ions are confined within these pores, they are no longer fully solvated by water. Instead, they are under-coordinated, meaning they are not entirely surrounded by water molecules. This change in their coordination state significantly alters their catalytic properties, making them more active in promoting certain reactions.
The study primarily focuses on the O-demethylation of guaiacol, which involves the removal of its methyl group (-CH3), resulting in the formation of catechol and methanol. This reaction is of great significance in the context of biorefinery, a forward-looking industrial process in which biomass waste (such as wood scraps, straws, and grass) is converted into building blocks for the chemical industry. These chemicals, currently derived from oil refining, are essential for the production of a wide range of everyday goods, from plastics to pharmaceuticals, to serve society’s needs.
Through a combined theoretical and experimental investigation of the guaiacol O-demethylation reaction, the researchers discovered that hydronium ions confined within small spaces are more active as catalysts than those in bulk water. This increased catalytic activity is attributed to a combination of factors: the undercoordination of the hydronium ions and the spatial organization of the reactants in relation to the catalyst. While the former is less dependent on the type of zeolite used, the latter is influenced by both the zeolite’s framework topology and the amount of water present.
These fundamental findings offer valuable insights into the atomistic mechanisms at play and pave the way for the rational design of more efficient catalysts for biomass conversion reactions, to make the transition from a society based on fossil to renewable and recycled carbon.
The study, now published in Nature Catalysis, is born within the collaborative Excellence of Science Project Biofact (https://www.biofact.be), promoting the development of a complete biorefinery to convert wood in value-added chemicals.
The article can be read at the publisher’s website: https://doi.org/10.1038/s41929-024-01282-6
A research briefing is available here: https://doi.org/10.1038/s41929-025-01296-8
CMM authors: Massimo Bocus, Elias Van den Broeck, Louis Vanduyfhuys, Veronique Van Speybroeck