In-situ quick XAFS measurements to unveil reaction mechanisms. X-rays were passed through a reacting sample under the influence of microwaves. The team discovered that a mononuclear intermediate species was important for the rapid formation of hexaniobate. Credit: Tokyo Metropolitan University

Researchers from Tokyo Metropolitan University have successfully traced the mechanism behind how an industrially important "superbase" catalyst is synthesized in a faster, microwave-assisted reaction. They took measurements using X-rays while the reaction occurred, uncovering how small precursor molecules were formed first before they clustered to create the final product.

Their insights promise finer control over a promising technology for speeding up chemical synthesis in industry. The study is published in the journal Catalysis Today.

Industrial importance of polyoxometalates

Polyoxometalates are industrially important compounds used to catalyze chemical reactions, from the synthesis of drugs to the fixation of carbon dioxide.

Their ability to speed up reactions is largely down to their intricate molecular structure, a jigsaw of metal oxide ions assembled into isolated, cage-like clusters. One of these, a hexaniobate ion (six niobium atoms per cluster), is known to be a superbase, compounds with an especially strong affinity to protons which are invaluable in organic catalysis.

Recently, a process has been introduced to produce hexaniobate rapidly and at high purity using microwaves.

Conventional methods require more than 24 hours at elevated temperature; with the help of microwaves, reaction times can be kept to within ten minutes. While this is good news for industry, the mechanism is not well understood.

Uncovering the reaction mechanism with X-rays

A team led by Professor Seiji Yamazoe from Tokyo Metropolitan University has now used X-ray absorption measurements to uncover the sequence of events which take place when hexaniobate clusters are formed in such a short period of time.

Their measurements were "in-situ," taken inside a reacting sample as it takes place, and fast, letting them distinguish individual processes before the final product is made. Specifically, they focused on X-ray absorption fine structure (XAFS), which can reveal changes in molecular structure.

Starting with a solution of niobium oxide, their measurements over time revealed how mononuclear niobium species (those containing only one niobium atom) were formed first at low temperature as the sample was heated.

When the sample hit around 160 degrees Celsius, these species began to cluster, forming a precursor from which the final hexaniobate product was able to rapidly form.

Benefits of faster synthesis and future implications

The value of a shorter reaction time is not only efficiency, but a better product. Hexaniobate anions are produced as a complex with a cation, tetrabutyl ammonium (TBA), which can break down over time and bind with the cluster, effectively polluting the sites on the anion where reactions can occur.

The team’s insights into the process promise tighter control over the process, a purer product, and better performance for an industrially important catalyst.

More information: Nattamon Panichakul et al, Mechanism of synthesizing hexaniobate cluster by microwave-assisted hydrothermal reaction, Catalysis Today (2026). DOI: 10.1016/j.cattod.2025.115593

Citation: Tracing the quick synthesis of an industrially important catalyst (2025, December 22) retrieved 22 December 2025 from https://phys.org/news/2025-12-quick-synthesis-industrially-important-catalyst.html

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