Hu Haitao, Nie Yunqing, Tao Yuewen, Huang Wenyu, Qi Long, Nie Renfeng
School of Chemical Engineering, Zhengzhou University, Zhengzhou 450001, China.
School of Chemistry and Chemical Engineering, Hubei University, Wuhan 430062, China.
Sci Adv. 2022 Jan 28;8(4):eabl9478. doi: 10.1126/sciadv.abl9478.
Catalytic dehydrogenation enables reversible hydrogen storage in liquid organics as a critical technology to achieve carbon neutrality. However, oxidant or base-free catalytic dehydrogenation at mild temperatures remains a challenge. Here, we demonstrate a metal-free carbocatalyst, nitrogen-assembly carbons (NCs), for acceptorless dehydrogenation of N-heterocycles even at ambient temperature, showing greater activity than transition metal-based catalysts. Mechanistic studies indicate that the observed catalytic activity of NCs is because of the unique closely placed graphitic nitrogens (CGNs), formed by the assembly of precursors during the carbonization process. The CGN site catalyzes the activation of C─H bonds in N-heterocycles to form labile C─H bonds on catalyst surface. The subsequent facile recombination of this surface hydrogen to desorb H allows the NCs to work without any H-acceptor. With reverse transfer hydrogenation of various N-heterocycles demonstrated in this work, these NC catalysts, without precious metals, exhibit great potential for completing the cycle of hydrogen storage.
催化脱氢能够实现液体有机物中可逆的氢储存，是实现碳中和的一项关键技术。然而，在温和温度下进行无氧化剂或无碱的催化脱氢仍然是一个挑战。在此，我们展示了一种无金属的碳催化剂，即氮组装碳（NCs），即使在室温下也能实现N-杂环的无受体脱氢，其活性高于过渡金属基催化剂。机理研究表明，观察到的NCs的催化活性归因于独特的紧密排列的石墨氮（CGNs），它是在碳化过程中由前驱体组装形成的。CGN位点催化N-杂环中C─H键的活化，在催化剂表面形成不稳定的C─H键。随后，该表面氢的快速重组以解吸H，使得NCs能够在没有任何氢受体的情况下工作。通过本工作中展示的各种N-杂环的反向转移氢化反应，这些不含贵金属的NC催化剂在完成氢储存循环方面具有巨大潜力。
