Selective dinitrogen binding to transition metal ions mainly covers two strategic domains: biological nitrogen fixation catalysed by metalloenzyme nitrogenases and adsorptive purification of natural gas and air. Many transition metal–dinitrogen complexes have been envisaged for biomimetic nitrogen fixation to produce ammonia3. Inspired by this concept, here we report mesoporous metal–organic framework materials containing accessible Cr(III) sites, able to thermodynamically capture N₂ over CH₄ and O₂. This fundamental study integrating advanced experimental and computational tools confirmed that the separation mechanism for both N₂/CH₄ and N₂/O₂ gas mixtures is driven by the presence of these unsaturated Cr(III) sites that allows a much stronger binding of N₂ over the two other gases. Besides the potential breakthrough in adsorption-based technologies, this proof of concept could open new horizons to address several challenges in chemistry, including the design of heterogeneous biomimetic catalysts through nitrogen fixation.

Nature Materials (2016) doi:10.1038/nmat4825
Received 05 June 2016 Accepted 15 November 2016 Published online 19 December 2016

http://www.nature.com/nmat/journal/vaop/ncurrent/full/nmat4825.html