Compound with positively charged clusters could be a useful catalyst – study

The accidentally discovered compound will likely lead to a number of scientific developments.

Lab technician using microscope (photo credit: INGIMAGE / ASAP)
Lab technician using microscope
(photo credit: INGIMAGE / ASAP)

A novel cluster compound that could be used as a catalyst has been discovered by researchers at Kyoto University’s Institute for Integrated Cell-Material Sciences (ICEMS).

The cationic cluster (named HSbOI), which differs from the majority of metal-oxo clusters due to its positive charge, features acidic protons that enable it to be an “excellent solid acid catalyst,” according to a peer-reviewed study published in Science Advances.

Traditional polyoxometalate compounds, which carry a negative charge, contain large metal-oxide clusters. These compounds have a variety of uses in products ranging from medicines to flash memory devices, a press release from ICEMS explains.  

What makes these compounds unique?

Unlike polyoxometalates, the compound that researchers described in the study is a hydroxy-iodide with large clusters that are positively charged. Accordingly, HSbOI is one of only a small number of similar compounds that have been studied. 

 Kyoto University  (credit: Wikimedia Commons) Kyoto University (credit: Wikimedia Commons)

Researchers who discovered the compound believe that the results have significant implications. “This finding may open up new possibilities in the design of solid-state catalysts,” according to Hiroshi Kageyama, a chemist at Kyoto University.

An accidental discovery

HSbOI was discovered accidentally, like many other significant scientific breakthroughs. Kageyama and his colleague, Ryu Abe, were in the midst of a years-long mission to develop new compounds that can absorb light for photocatalysis. They attempted to replace the chlorine atom of a compound with iodine and expected to create a material containing 22 atoms in its unit cell. Instead, they developed HSbOI, which holds 800 atoms.

Kageyama and Abe collaborated with Artem Abakumov and Joke Hadermann at the University of Antwerp, using a state-of-the-art electron microscopy technique that uncovered the large clusters within the compound. 

For the study, researchers created a powder sample of HSbOI that they dissolved into a mixture and stirred for one hour at 75°C (167°F) followed by another hour at 0°C (32°F). Researchers then recovered the product through filtration before washing and dehydrating it.

The discovery of HSbOI could result in significant scientific developments. Positively charged clusters such as those analyzed in the study may lead to new design possibilities for solid-state catalysts — substances that increase the rate of chemical reactions. 

Furthermore, the clusters can be structurally modified to synthesize oxide cage structures as well as higher-order structures, the study explains. Dissolving and isolating these clusters will also be useful. The researchers hypothesized that, once the clusters are dissolved, they will be able to be used for homogenous catalysis and as building blocks for organic-inorganic composites. 

Possibilities for the use of HSbOI clusters are numerous. “In science, the discovery of [a] new material or molecule can create a new science,” Kayegama stated. “I believe that these new positively charged clusters have great potential.”