Array-Based Clusters of Copper with Largely Exposed Metal Sites for Promoting Catalysis
Xiaoxuan Xu, Ying Liu, Fang Sun, Yanyuan Jia, Qing‐Hua Xu, Jiaqi Tang, Zhen‐Lang Xie, Jing Sun, Simin Li, Qing Tang, Shuo Guo, Hui Shen, Nanfeng Zheng
Abstract
Most ligand-stabilized metal nanoclusters feature a core–shell or polyhedron-derived metal framework, in which the metal active sites would be blocked by either metal–ligand interfacial shells or surface passive units. We report, in this work, a strategy of largely exposing metal sites and thus promoting catalysis via constructing metal nanoclusters with array-based geometry. Exampled here are a pair of Cu 8 clusters with polyhedron-derived ([Cu 8 (RS) 6 (PPh 3 ) 4 (MeCN) 4 H] +, where RS is 3,5-bis(trifluoromethyl)benzenethiol) and array-based ([Cu 8 (Tf-dpf) 4 (NO 3 ) 2 ](NO 3 ) 2, Tf-dpf is N, N ′-di(5-trifluoromethyl-2-pyridyl) formamidinate) structure, respectively. In sharp contrast to the cubic Cu 8 cluster whose metal core has been totally covered by ligands, the array-based analogue displays largely uncoordinated metal sites. As a result, the array-based Cu 8 cluster exhibits significantly enhanced activity in catalytic hydrogenation reactions in comparison to the cubic one. In addition, the array-based Cu 8 cluster shows excellent catalytic performance in the “aldehyde–acetylene–amine” A 3 -coupling reaction for the synthesis of propargylamines. The reaction can be converted almost perfectly with a rather low amount of cluster, which further reflects its potential catalytic application.