In July 2022, our research paper was published in Nature. This study, entitled “Nitrogen reduction by the Fe sites of synthetic [Mo₃S₄Fe] cubes”, demonstrates the first catalytic reduction of N₂ by synthetic metal-sulfur compounds and provides clues on how N₂ is captured by the enzyme in nature and why the protein matrix around the N₂-binding site is needed.

The reduction of N₂ is the key elementary step to provide nitrogen atoms in amino acids and DNA and is hence indis- pensable for every form of life. Nitrogenase is the enzyme for this process, and at an atomic level, FeMoco (top in the figure) consisting of iron (Fe)-molybdenum (Mo)-sulfur (S)-carbon (C) is in charge of the difficult N₂ reduction. Due to the structural complexity of FeMoco, the key elements of N₂ reduction have remained unresolved. In this study, Ohki et al. predicted the structure of N₂-bound FeMoco (left bottom of the figure) and the function of the protein, and synthesized cubic Mo-Fe-S compounds as simplified models (right bottom of the figure). This study not only represents the first step toward N₂ reduction by artificial metal-sulfur compounds, but also a good example of how the utilities of metal-sulfur compounds can be expanded by learning from enzymes and applying appro- priate molecular design.