News Source: School of Chemistry and Chemical Engineering

Editor: News Agency of BIT

Translator: News Agency of BIT, Yang Ruiguang

Recently, associate professor Ma Jiabi’s team, from the School of Chemistry and Chemical Engineering, Beijing Institute of Technology (BIT), has conducted intensive study on the reactivity and cluster structure of N2 and NbB3O2− gas-phase clusters through mass spectrometry experiments and high-precision quantum chemistry calculations, and has successfully constructed the N2 catalyst containing double active sites and a single early transition metal atom, realizing the activation and transformation of N2 at room temperature. Its activation mode is metal-ligand activation (MLA). The result is published in the international authoritative journal The Journal of Physical Chemistry Letters (2021, 12, 6313-6319) with the title of "Nitrogen Activation and Transformation on Monometallic Niobium Boron Oxide Cluster Anions at Room Temperature: A Dual-Site Mechanism". Doctoral student Wang Ming of the School of Chemistry and Chemical Engineering is the first author of the paper, and associate professor Ma Jiabi of BIT is the corresponding author.

Because of the high stability of N2, the activation and transformation of N2 at room temperature remain extremely challenging. The current literature reports on N2 activation and transformation mediated with gas-phase metal ions are mostly about the application of the group VIII metals (such as Fe, Ni, Ru, etc.), and most of their active sites are polynuclear metal ions, while there are few reports on the early transition metals. In 2019, the team of Ma Jiabi discovered that Ta3N3H− and Ta3N3− clusters with 2 and 3 Ta atoms at active sites can fully activate N2 molecules and generate adsorption products Ta3N5H− and Ta3N5− (J. Am. Chem. Soc. 2019, 141, 12592-12600). Based on this finding, the team proposed the metal-ligand activation (MLA) mode in 2021, realizing the reaction of directly coupling N2 and CO2 molecules by NbH2− clusters at room temperature and the preparation of C−N bond from N2 and CO2. (J. Phys. Chem. Lett. 2021, 12, 3490-3496). However, the catalytic cycle has not been realized.

Figure 1: Proposed Catalytic Cycle for N2 Activation

Mediated with NbB3O2− Anions

With the support of Major Research Project of National Natural Science Foundation of China, the team of associate professor Ma Jiabi of the School of Chemistry and Chemical Engineering of our school， based on previous research， used mass spectrometry combining with quantitative calculations to design and synthesize the monometallic anion NbB3O2− cluster, which can efficiently convert N2 and produce two N-containing products, namely B3N2−/NbO and B3N2O2−/Nb, at room temperature. In this reaction system, the Nb atom serves as an adsorption site for N2; the B atom acts as the electron donor and break the N≡N bond by giving 2p electrons to N2; the Nb atom and the B3O2 unit act as the dual active center which can accomplish the efficient transfer of activated N atoms through the synergy of the two. Afterwards, DFT theory calculations suggest that NbO and Nb neutral clusters can continue to react with B3O− and B3O2− anions to generate NbB3O2− anions, realizing the catalytic cycle of the reaction. By introducing the main group element B to form the second active site, a monometallic cluster ion with dual active sites (Nb atom and B3O2 unit) is constructed to achieve the high-efficiency catalytic conversion of N2 to N-containing products. The catalytic mechanism can also apply to the aforementioned MLA model, and it opens up new ideas for the use of early transition metals to construct monometallic catalysts for nitrogen conversion at room temperature.

Link to the related paper: https://doi.org/10.1021/acs.jpclett.1c01633