Single-atom heterogeneous catalysts based on distinct carbon nitride scaffolds
Single-atom heterogeneous catalysts based on distinct carbon nitride scaffolds
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DOI：
10.1093/nsr/nwy048
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发表时间：
2018-09-01
影响因子：
20.6
通讯作者：
Perez-Ramirez, Javier
中科院分区：
文献类型：
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作者：
Chen, Zupeng;Vorobyeva, Evgeniya;Perez-Ramirez, Javier
整合大杂环的碳氮化合物由于其丰富的电子结构，作为稳定金属原子的宿主具有独特的潜力。迄今为止，只研究了石墨七嗪基聚合物。在这里，我们证明了钯原子可以有效地隔离在其他氮化碳支架上，包括线性melem低聚物和聚三嗪/七嗪亚胺。增加的金属摄取与较大的腔尺寸和聚酰亚胺结构中氯离子的存在有关。通过x射线光电子能谱和密度泛函理论证明，改变主体结构会导致金属的平均氧化态发生显著变化，这种变化可以通过离子种类的交换来调节。对2-甲基-3-丁-2-醇半加氢反应的评价表明，活性与钯的氧化程度呈负相关，低聚物的活性最高。这些发现为氮化碳结构对金属稳定性的影响提供了新的机制见解。
Carbon nitrides integrating macroheterocycles offer unique potential as hosts for stabilizing metal atoms due to their rich electronic structure. To date, only graphitic heptazine-based polymers have been studied. Here, we demonstrate that palladium atoms can be effectively isolated on other carbon nitride scaffolds including linear melem oligomers and poly(triazine/heptazine imides). Increased metal uptake was linked to the larger cavity size and the presence of chloride ions in the polyimide structures. Changing the host structure leads to significant variation in the average oxidation state of the metal, which can be tuned by exchange of the ionic species as evidenced by X-ray photoelectron spectroscopy and supported by density functional theory. Evaluation in the semi-hydrogenation of 2-methyl-3-butyn-2-ol reveals an inverse correlation between the activity and the degree of oxidation of palladium, with oligomers exhibiting the highest activity. These findings provide new mechanistic insights into the influence of the carbon nitride structure on metal stabilization.