Tuning the coordination environment of single-atom catalyst M-N-C towards selective hydrogenation of functionalized nitroarenes

Fine-tuning of the coordination environment of single-atom catalysts (SACs) is effective to optimize their catalytic performances, yet it remains challenging due to the vulnerability of SACs. Herein, we report a new approach to engineering the coordination environment of M-N-C (M = Fe, Co, and Ni) SACs by using glutamic add as the N/C source and pyrolysis atmosphere as a regulator. Compared with that in N-2, NH3 was able to promote the doping of N at T< 700 degrees C yet etch the N-species at higher temperatures, by which the M-N coordination number (CN) and the electronic structure were delicately tuned. It was found that the electron density of Ni single atoms increased with the decrease of Ni-N CN. As a consequence, the capability of Ni-N-C to dissociate H-2 was greatly enhanced and a higher catalytic activity in chemoselective hydrogenation of functionalized nitroarenes was achieved. Moreover, this modulation method could be applied to other transition metals including Fe and Co. In particular, the as-synthesized Co-N-C SAC afforded a turnover frequency of 152.3 h(-1 )with 99% selectivity to 3-vinylaniline in the hydrogenation of 3-nitrostyrene, which was the highest ever reported thus far and was at least one order of magnitude more active than state-of-the-art noble-metal-free M-N-C catalysts, demonstrating the great potential of engineering the coordination environment of SACs.

Automated summary

Fine-tuning the coordination environment of single-atom catalysts (SACs) using glutamic acid as the N/C source and pyrolysis atmosphere as a regulator has been shown to effectively optimize catalytic performances. This approach delicately tunes the M-N coordination number and electronic structure, leading to enhanced catalytic activity. Particularly, the Co-N-C SAC synthesized through this method exhibited significantly higher turnover frequency and selectivity in hydrogenation reactions compared to state-of-the-art noble-metal-free M-N-C catalysts.