Ren Peng, Li Qinglin, Song Tao, Yang Yong
CAS Key Laboratory of Bio-Based Materials, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao 266101, China.
University of Chinese Academy of Sciences, Sino-Danish College, Beijing 100049, China.
ACS Appl Mater Interfaces. 2020 Jun 17;12(24):27210-27218. doi: 10.1021/acsami.0c05100. Epub 2020 Jun 2.
M-N-C catalysts have attracted considerable attention in the fields of energy storage and conversion as well as catalysis over the past decades. However, the current synthetic strategies for fabricating M-N-C catalysts via high-temperature pyrolysis unavoidably lead to a structural heterogeneity with the presence of a mixture of species including atomically dispersed M-N moieties and inorganic metal-containing particles, which not only decreases the atomic utilization but also clouds the accurate understanding of the nature of the catalytically active sites. Herein, we first report a straightforward and cost-effective preparation strategy for fabricating a Cu-N-C catalyst with atomically dispersed and coordinately unsaturated Cu-N moieties on hierarchically N-doped porous carbon (Cu/NC-800) without formation of any metal-containing phases. Cu/NC-800 exhibits outstanding catalytic performance for Glaser-Hay coupling of terminal alkynes under mild and sustainable conditions, which surpass those of the state-of-the-art catalysts. A broad set of (un)symmetrical aryl-aryl, aryl-alkyl, and alkyl-alkyl 1,3-diynes were selectively synthesized in high yields with good tolerance of various functional groups. More importantly, the Cu/NC-800 could be easily reused with good maintenance of the activity and atomic dispersion of Cu in the structure. Experimental results and theoretical calculations reveal that the low N coordination number of single-atom Cu sites in Cu-N exhibit a preferential adsorption to terminal alkyne; meanwhile, the adjacent pyridinic N sites on the carbon matrix facilitate the deprotonation of the adsorbed alkyne to generate the key intermediate Cu-acetylide species, thus synergistically boosting the reaction. Therefore, this work not only provides an alternative facile synthetic strategy for fabricating atomically dispersed M-N-C catalysts but also represents a significant advance for accessing (un)symmetrical 1,3-diynes from Glaser-Hay coupling.
在过去几十年中，M-N-C催化剂在能量存储与转换以及催化领域引起了相当大的关注。然而，目前通过高温热解制备M-N-C催化剂的合成策略不可避免地导致结构不均匀，存在包括原子分散的M-N部分和含无机金属颗粒在内的多种物种混合物，这不仅降低了原子利用率，还模糊了对催化活性位点本质的准确理解。在此，我们首次报道了一种直接且经济高效的制备策略，用于在分级N掺杂多孔碳（Cu/NC-800）上制备具有原子分散且配位不饱和的Cu-N部分的Cu-N-C催化剂，且不形成任何含金属相。Cu/NC-800在温和且可持续的条件下对末端炔烃的格拉泽-海偶联表现出出色的催化性能，超过了现有催化剂。一系列广泛的（非）对称芳基-芳基、芳基-烷基和烷基-烷基1,3-二炔以高产率被选择性合成，对各种官能团具有良好的耐受性。更重要的是，Cu/NC-800可以很容易地重复使用，并且在结构中Cu的活性和原子分散性能够得到良好保持。实验结果和理论计算表明，Cu-N中单个原子Cu位点的低N配位数对末端炔烃具有优先吸附作用；同时，碳基体上相邻的吡啶N位点促进了吸附炔烃的去质子化，生成关键中间体Cu-乙炔化物物种，从而协同促进反应。因此，这项工作不仅为制备原子分散的M-N-C催化剂提供了一种简便的合成策略，而且在通过格拉泽-海偶联获得（非）对称1,3-二炔方面也取得了重大进展。
