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CNRS researchers use boron radicals to convert nitrogen to ammonia in solution; mild ammonia synthesis

Ammonia is obtained industrially using the Haber–Bosch process, which requires a lot of energy and hydrogen gas. A team of researchers headed by Nicolas Mézailles of the Université Paul Sabatier, CNRS, in Toulouse, France has developed a much milder approach using reactive boron compounds.

The boron compounds can efficiently target atmospheric nitrogen and convert it to ammonium chloride after the addition of an acid. This conversion takes place in solution, at room temperature, and without the need for metals or hydrogen gas. An open-acess paper on their work is published in the journal Angewandte Chemie.


Bennaamane et al.

Nitrogen makes up 77% of the air we breathe, and so, in theory, it is virtually infinitely available for ammonia synthesis. However, in practice, it only reacts extremely slowly with other elements. In the Haber–Bosch process, which was developed more than 100 years ago, metal catalysts accelerate this sluggish reaction. These catalysts activate the nitrogen which is then reacted with hydrogen under high pressure and temperature, producing ammonia. Haber-Bosch production of ammonia generates around 1.6% of global CO2 emissions.

To date, microbiological methods for nitrogen fixation have been the predominant milder alternative proposed for the Haber–Bosch process. However, exploiting bacteria for biotechnological ammonia production is still quite inefficient.

The CNRS team reasoned that the use of high-energy radicals might provide a kinetically and thermodynamically favorable alternative pathway to nitrogen functionalization.

The team’s theoretical calculations highlighted boron-centered radicals as suitable candidates. The researchers produced these boron-centered radicals by adding a strong reducing agent to organic boron halides. The resulting substances converted molecular nitrogen at room temperature to borylamines, which in turn reacted with aqueous acid to give ammonium chloride.

The boron-centered radicals efficiently break down the stable triple bond in molecular nitrogen, making it possible to functionalize molecular nitrogen under mild conditions. This radical-based approach opens up further possibilities for ammonia production without having to rely on fossil-based raw materials.


  • S. Bennaamane, B. Rialland, L. Khrouz, M. Fustier-Boutignon, C. Bucher, E. Clot, N. Mézailles (2022) “Ammonia Synthesis at Room Temperature and Atmospheric Pressure from N2: A Boron-Radical Approach” Angew. Chem. Int. Ed. doi: 10.1002/anie.202209102


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