Industrial production of vinyl chloride through acetylene hydrochlorination is a dominating technique in coal-rich areas, but its development is severely restricted by the use of toxic mercury chloride (HgCl 2 ) catalyst. Inspired by the fact that doped carbon materials active in acetylene hydrochlorination often have good performance in the oxygen reduction reaction, a series of cobalt and nitrogen co-doped porous carbon catalysts prepared by pyrolysis of bimetallic ZIFs based on ZIF-8 and ZIF-67 under N 2 were applied in acetylene hydrochlorination. The catalytic activities of the co-doped catalysts varied with Co addition, and the highest acetylene conversion could be up to 83% with a space velocity of 2.6 ml g −1 min −1 at 220°C when a small amount of cobalt was introduced. Results of several characterizations confirmed the existence of Co–N x in the co-doped carbons, pointing out that this coordination structure makes the catalysts have better ability to adsorb and activate C 2 H 2 . Density functional theory calculation finally proved that C atom adjacent to the N atom in Co–N 4 structure is the primary active site in co-doped catalysts with high activity. We also conclude that the decreased N content caused by Co 2 N decomposition and the coordination structure change of Co–N x should be responsible for the gradually worsening performances of the carbon catalysts with further Co addition. Our study provides a new route for improving the performance of N-doped carbon material in acetylene hydrochlorination and thus enhances its potential for practical application.
The electronic state modulation of catalytic active sites governs the oxidation/reduction activation pathway of peroxymonosulfate (PMS), however, directional singlet oxygen ( 1 O 2 ) generation via establishing electron-depleted active center remains challenging. Herein, we propose an innovative axial coordination strategy to engineer atomically dispersed Co-N x moieties on MXene substrates, creating a Co SA -N 2 O 1 /MXene catalyst with precisely modulated electron-depleted sites. The tailored electronic configuration redirects 2,4-dichlorophenol degradation from radical-dominated pathway (Co SA -N 4 counterpart without axial O modulation) to 1 O 2 -driven mechanism with 90.5% contribution, achieving up to 5.1-fold activity enhancement, even outperforming most state-of-the-art Fenton-like systems. The charge density redistribution and greater density of states near Fermi level accelerate PMS activation to selective generation of 1 O 2 . It also demonstrates exceptional environment robustness and high stability for treating real lake water. Our findings advance atomic-level insights into PMS activation and establish a novel paradigm of axial coordination engineering for designing next-generation single-atom catalysts.
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