Tao Xueqin, Long Ran, Wu Di, Hu Yangguang, Qiu Ganhua, Qi Zeming, Li Benxia, Jiang Ruibin, Xiong Yujie
Department of Chemistry, School of Science, Zhejiang Sci-Tech University, Zhejiang, 310018, P. R. China.
Hefei National Laboratory for Physical Sciences at the Microscale, iChEM (Collaborative Innovation Center of Chemistry for Energy Materials), School of Chemistry and Materials Science and National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei, Anhui, 230026, P. R. China.
Small. 2020 Oct;16(43):e2001782. doi: 10.1002/smll.202001782. Epub 2020 Oct 4.
Single-atom (SA) catalysis bridging homogeneous and heterogeneous catalysis offers new opportunities for organic synthesis, but developing SA catalysts with high activity and stability is still a great challenge. Herein, a heterogeneous catalyst of Pd SAs anchored in 3D ordered macroporous ceria (Pd-SAs/3DOM-CeO ) is developed through a facile template-assisted pyrolysis method. The high specific surface area of 3DOM CeO facilitates the heavily anchoring of Pd SAs, while the introduction of Pd atoms induces the generation of surface oxygen vacancies and prevents the grain growth of CeO support. The Pd-SAs/3DOM-CeO catalyst exhibits excellent activity toward Suzuki coupling reactions for a broad scope of substrates under ambient conditions, and the Pd SAs can be stabilized in CeO in long-term catalytic cycles without leaching or aggregating. Theoretical calculations indicate that the CeO supported Pd SAs can remarkably reduce the energy barriers of both transmetalation and reductive elimination steps for Suzuki coupling reactions. The strong metal-support interaction contributes to modulating the electronic state and maintaining the stability of Pd SA sites. This work demonstrates an effective strategy to design and synthesize stable single-atom catalysts as well as sheds new light on the origin for enhanced catalysis based on the strong metal-support interactions.
单原子（SA）催化架起了均相催化和多相催化之间的桥梁，为有机合成提供了新机遇，但开发具有高活性和稳定性的单原子催化剂仍然是一项巨大挑战。在此，通过一种简便的模板辅助热解方法，开发出一种锚定在三维有序大孔氧化铈中的钯单原子多相催化剂（Pd-SAs/3DOM-CeO）。三维有序大孔氧化铈的高比表面积有助于钯单原子的大量锚定，而钯原子的引入诱导了表面氧空位的产生，并防止了氧化铈载体的晶粒生长。Pd-SAs/3DOM-CeO催化剂在环境条件下对广泛底物的铃木偶联反应表现出优异活性，并且钯单原子在长期催化循环中能够稳定在氧化铈中，不会浸出或聚集。理论计算表明，氧化铈负载的钯单原子能够显著降低铃木偶联反应的转金属化和还原消除步骤的能垒。强金属-载体相互作用有助于调节电子态并维持钯单原子位点的稳定性。这项工作展示了一种设计和合成稳定单原子催化剂的有效策略，同时也基于强金属-载体相互作用为增强催化作用的起源提供了新见解。
