News Source & Photographer: Ma Jiabi, School of Chemistry and Chemical Engineering

Editor: News Agency of BIT

Translator: News Agency of BIT, Zhang Langbo

Recently, associate professor Ma Jiabi's team, from the School of Chemistry and Chemical Engineering, Beijing Institute of Technology (BIT), studied the reactivity and structure of N₂and CO₂with NbH₂- gas-phase clusters by using mass spectrometry (MS), anion photoelectron spectroscopy (PES), and quantum-chemical calculations, enabled the direct coupling of N₂and CO₂to form the C-N bond at room temperature, and revealed a novel N₂activation mode——Metal-Ligand Activation（MLA）. The related results were published in the international authoritative journal The Journal of Physical Chemistry Letters(2021, 12, 3490-3496) under the title of "Dinitrogen and Carbon Dioxide Activation to Form C–N Bonds at Room Temperature: A New Mechanism Revealed by Experimental and Theoretical Studies". Wang Ming (PhD student of School of Chemistry and Chemical Engineering), Chu Lanye (master student) and Li Ziyu (Institute of Chemistry, Chinese Academy of Sciences) are co-first authors of this paper. Ma Jiabi (associate professor of BIT) and Hu Lianrui (teacher of Xihua University) are co-corresponding authors of this paper.

N₂and CO₂are very inert small molecules. It is really challenging to activate and couple N₂and CO₂under mild conditions to directly form C-N bonds to convert them into valuable chemical products. At present, only a few condensed-phase species can directly couple N₂and CO₂to form C–N bond-containing compounds, and all of them require external fields. For example, urea is synthesized by photolysis and synthesis of isocyanate and electrocatalytic coupling of N₂and CO₂and so on. So far, studies on N₂activation and transformation mediated by metallic ions in the gas-phase have been reported, in which the cleavage of N≡N bond usually requires multinuclear transition metal atoms as the active sites . In 2019, Ma Jiabi's team found that Ta₃N₃H - and Ta₃N₃- clusters can completely activate N₂molecules and form adsorption Ta₃N₅H− and Ta₃N₅− products. During the reaction, the active sites of N₂reduction were 2 and 3 Ta atoms respectively（ J. Am. Chem. Soc. 2019, 141 , 12592-12600）. Based on the activation of N₂, if the further transformation of N₂into C−N bonds can be achieved, it will be of profound significance for the metal-organic or coordination chemistry.

Fig. 1. Schematic diagram of NbH2 - sequential reaction with N2 and CO2

With the support of the National Natural Science Foundation of China's major research program, and based on the previous research, the team of associate professor Ma Jiabi from the School of Chemistry and Chemical Engineering in our university activated N₂and CO₂successively to form the C-N bond at room temperature. Further theoretical calculations indicate that the most favorable steps for the formation of C−N bonds through the coupling between CO₂and N₂under mild conditions are as follows: 1) N₂preactivation, 2) CO₂activation, 3) C−N bond formation with simultaneous N−N bond fracture. During N₂activation, the 2p-orbital of C interacts with the 2p-orbital of N instead of the transition metal d-orbital. Only one non-noble metal Nb atom is necessary to activate N₂, while the adjacent C atom from CO₂is an electron reservoir, which is used to receive and donate electrons. This is the first gas-phased cluster which couples N₂and CO₂at room temperature. This work reveals a novel and important N₂activation mode -- Metal-Ligand Activation (MLA), which will help to develop new strategies for the design of single-metal atom catalysts.

Besides, the team, in cooperation with professor Xiao Shoufeng from Zhejiang University, successfully combined the cluster model with molecular sieve catalyst, and made a series of progress and breakthroughs in the preparation of chemical products by aerobic dehydrogenation of propane. For example, in a paper published in ACS Catal (2020, 10 , 10559-10569，IF=""12.35"”), they found and demonstrated that in the MnO X-CeO₂system, by regulating the surface oxygen of the catalyst through strong oxi-carrier interaction (SOSI), the combustion catalyst can be converted into a selective dehydrogenation catalyst, and the high activity site is derived from the interfacial oxygen. What’s more, in the propane dehydrogenation reaction, the unit point B was synthesized and proved to be the active center in the reaction, which was different from the common catalyst containing B-O-B oligomer. This study breaks the traditional cognition of boron based catalyst and provides a new idea for the industrialization of aerobic dehydrogenation of propane to propylene. This achievement was published in the paper entitling "Isolated Boron in Zeolite for oxidative dehydrogenation of propane" in Science (372, 76-80). Professor Ma Jiabi and doctoral student Wang Ming in BIT are the collaborators.

Links to the articles:

https://pubs.acs.org/doi/10.1021/acs.jpclett.1c00183

https://dx.doi.org/10.1021/acscatal.0c02782

https://science.sciencemag.org/content/372/6537/76