Lin Tian, Cao Zhouwen, Pei Junqi, Wang Bohua, Liu Hanlin, Tu Bin, Yang Caoyu, Zheng Fengbin, Chen Wenxing, Fang Qiaojun, Liu Wei, Tang Zhiyong, Li Guodong
School of Chemical Science, University of Chinese Academy of Sciences, Beijing 100049, P. R. China.
Chinese Academy of Sciences (CAS) Key Laboratory of Nanosystem and Hierarchical Fabrication, CAS Center for Excellence in Nanoscience, National Center for Nanoscience and Technology, Beijing 100190, P. R. China.
J Am Chem Soc. 2025 Apr 9;147(14):11975-11987. doi: 10.1021/jacs.4c18288. Epub 2025 Mar 27.
The chemoselective hydrogenation of halonitrobenzenes to haloanilines is of great importance but remains challenging to simultaneously achieve high catalytic activity, excellent selectivity, and good reusability, especially for -substituted substrates. This is due to the occurrence of hydrogenolysis of halogen groups, as well as the easy migration and aggregation of active species on the catalyst surface during the hydrogenation of nitro groups. In this study, we integrate Pt nanoparticles (NPs) with auxiliary Co-N single sites from a porphyrinic metal-organic framework [known as PCN-221(Co)] in a sandwiched nanostructure as a catalyst for the chemoselective hydrogenation of -halonitrobenzenes at 80 °C and 1 MPa H in a 50 mL batch microreactor. This sandwiched catalyst achieves 97.3% selectivity for -chloroaniline at nearly complete conversion of -chloronitrobenzene, with an exceptionally high turnover frequency (TOF) of 11,625 h and good reusability over ten cycles, outperforming state-of-the-art heterogeneous supported metal catalysts. Theoretical and experimental investigations reveal that the nitro group in -chloronitrobenzene is preferentially hydrogenated by Pt NPs, while the -chloro group is selectively adsorbed by Co-N single sites in PCN-221(Co), preventing its hydrogenolysis and enhancing selectivity for -chloroaniline. Furthermore, the PCN-221(Co) shell in the sandwiched catalyst plays a key role in enriching -chloronitrobenzene and stabilizing the supported Pt NPs, thus leading to high catalytic activity and good reusability. Additionally, at nearly complete conversion of -fluoronitrobenzene and -bromonitrobenzene, this sandwiched Pt catalyst displays 100% selectivity for -fluoroaniline with a TOF of 8680 h and 99.2% selectivity for -bromoaniline with a TOF of 5859 h, respectively. When - and -halonitrobenzenes are used as substrates, high activity and excellent selectivity for the corresponding haloanilines are also achieved by the sandwiched Pt catalysts.
卤代硝基苯化学选择性加氢制备卤代苯胺具有重要意义，但要同时实现高催化活性、优异的选择性和良好的可重复使用性仍具有挑战性，特别是对于对位取代的底物。这是由于卤代基团会发生氢解，以及在硝基加氢过程中活性物种在催化剂表面容易迁移和聚集。在本研究中，我们将铂纳米颗粒（NPs）与来自卟啉金属有机框架[即PCN - 221(Co)]的辅助钴 - 氮单位点整合到夹心纳米结构中，作为在50 mL间歇式微反应器中80 °C和1 MPa氢气条件下卤代硝基苯化学选择性加氢的催化剂。这种夹心催化剂在对氯硝基苯几乎完全转化时，对氯苯胺的选择性达到97.3%，具有11,625 h的超高周转频率（TOF），并且在十个循环中具有良好的可重复使用性，优于目前最先进的多相负载金属催化剂。理论和实验研究表明，对氯硝基苯中的硝基优先被铂纳米颗粒加氢，而氯基团被PCN - 221(Co)中的钴 - 氮单位点选择性吸附，从而防止其氢解并提高对对氯苯胺的选择性。此外，夹心催化剂中的PCN - 221(Co)壳层在富集对氯硝基苯和稳定负载的铂纳米颗粒方面起着关键作用，从而导致高催化活性和良好的可重复使用性。此外，在对氟硝基苯和对溴硝基苯几乎完全转化时，这种夹心铂催化剂对对氟苯胺的选择性分别为100%，TOF为8680 h，对对溴苯胺的选择性为99.2%，TOF为5859 h。当间位和邻位卤代硝基苯用作底物时，夹心铂催化剂也能实现对相应卤代苯胺的高活性和优异选择性。
