Alternative palladium (Pd)-based catalysts to toxic mercuric chloride catalysts in vinyl chloride manufacture via acetylene hydrochlorination is currently limited by the lack of efficient and durable active sites. Here, the catalytic behavior of Pd-based catalysts with tunable nanostructures and coordination bonds were investigated. The evolution of Pd entities were precisely regulated by controlled thermal treatment. Pyridinic nitrogen is shown to regulate the nanostructures and coordination bonds of Pd sites, improve the thermal stability of Pd atoms, promote the adsorption of acetylene and enrich hydrogen chloride. These results indicate that Pd single-atom is more active than Pd nanoparticle or Pd cluster. The catalytic performance of Pd single-atom catalyst can be further improved by substituting Pd-Cl bond with Pd-N bond, with PdN₂ identified as the efficient and durable active sites. Furthermore, the enrichment of hydrogen chloride enables the Pd single-atom catalysts to produce vinyl chloride via a non-hydrogen chloride excess method, which is a breakthrough in the existing industrial system. Our strategy for controlling the catalytic behavior of Pd sites is of a broad application prospect for the precise control and design of metal active sites.

通过氯乙烯生产中的有毒氯化汞催化剂的替代钯（Pd）基催化剂乙炔盐酸盐化目前由于缺乏有效和持久的活性位点而受到限制。在此，研究了具有可调纳米结构和配位键的Pd基催化剂的催化行为。通过控制热处理可精确调节Pd实体的演变。吡啶二价氮可调节Pd位点的纳米结构和配位键，提高Pd原子的热稳定性，促进乙炔的吸附并富集氯化氢。这些结果表明，Pd单原子比Pd纳米颗粒或Pd团簇更具活性。通过用PdN ₂取代Pd-Cl键和Pd-N键，可以进一步提高Pd单原子催化剂的催化性能。被确定为有效和持久的活动站点。此外，氯化氢的富集使Pd单原子催化剂能够通过非氯化氢过量法生产氯乙烯，这是现有工业系统的一项突破。我们控制Pd位点催化行为的策略对于精确控制和设计金属活性位点具有广阔的应用前景。