SHIRAI Laboratory's research paper, "Tailoring amorphous alumina catalysts with enriched five-coordinated aluminum via pH control," which reports on the synthesis of amorphous alumina catalysts rich in five-coordinated aluminum (Al(V)), has been highly acclaimed and selected for the Outside Front Cover of Catalysis Science & Technology, a journal published by the Royal Society of Chemistry in the United Kingdom.

Amorphous alumina, obtained from aluminum resources that are extremely abundant on Earth, is not only inexpensive and highly chemically stable, but also contains a large amount of a unique atomic arrangement known as five-coordinated aluminum (Al(V)) because it does not have a crystalline structure. Al(V) is an important structure, sometimes referred to as "Super Five," because it functions in catalytic reactions and serves as an anchor site for precious metals.

In this study, the research team sought to optimize both the quality and quantity of Al(V) sites by controlling the concentration and pH of buffer solutions during the formation process of aluminum hydroxide gel. As a result, they successfully developed a novel, highly active catalyst in which alumina itself functions as the catalyst.

Furthermore, through detailed analysis of solid-state NMR spectra, the team identified two distinct structures of Al(V): trigonal bipyramidal and square pyramidal. They also found that the square pyramidal structure contributes to the catalytic reaction. Based on these findings, under pH-optimized conditions using a 1 mM buffer solution, the team achieved 100% complete decomposition of ethyl acetate, a representative environmental pollutant among volatile organic compounds (VOCs), using only pure amorphous alumina.

Unlike previous studies, the pH-controlled amorphous alumina established in this research presents design principles for "precious-metal-free catalysts" that do not use any expensive precious metals. This achievement is expected to make a significant contribution to the realization of the SDGs by enabling lower-cost and higher-efficiency air purification technologies.