Ultrafine Pd Nanoparticles Anchored on Spherical Covalent Triazine Frameworks for the Selective Tandem Hydrogenation of Nitrobenzene and Benzaldehyde to Secondary Amines

• Published in: ACS sustainable chemistry & engineering Vol. 12; no. 40; pp. 14732 - 14746
• Main Authors: Gao, Mengmeng, He, Guoqiang, Long, Xiao, Wang, Shiyong, Guo, Zhen, Dong, Zhengping, Yuan, Kun
• Format: Journal Article
• Language: English
• Published: American Chemical Society 07.10.2024
• Subjects: tandem reaction; covalent organic frameworks; N-benzylaniline; Pd nanoparticles; P123
• DOI: 10.1021/acssuschemeng.4c05020
• ISSN: 2168-0485

The selective tandem one-pot synthesis of secondary amines via nitrobenzene and benzaldehyde coupling–hydrogenation is challenging due to side reactions. Herein, a covalent organic framework (COF)-based catalyst was fabricated by anchoring ultrafine Pd nanoparticles on a spherical COF material (Pd/DHTA-COF-P123). The surfactant P123 was used as a template during solvothermal synthesis to control the morphology of DHTA-COF-P123 via micellar encapsulation, which endowed the material with a large surface area. The spherical DHTA-COF-P123 support strengthened the metal–support interactions (SMSIs) and regulated the electronic state of Pd species to an electron-rich state, thereby improving catalytic hydrogenation. During Pd/DHTA-COF-P123-catalyzed nitrobenzene and benzaldehyde coupling–hydrogenation, 99.9% conversion of nitrobenzene and 99.6% selectivity for N-benzylaniline were obtained under mild reaction conditions. Theoretical calculations confirmed that the stronger SMSIs were responsible for the excellent activity of Pd/DHTA-COF-P123 in the tandem reaction, and the hydrogenation process was exothermic, which strengthened absorption. This work proposes a green strategy to fabricate an electron-rich Pd-based catalyst by enhancing SMSIs to catalyze the synthesis of secondary amines.