Yang Ge, Huang Jiajia, Gu Weizhi, Lin Zhongyuan, Wang Qingyu, Kang Rong, Liu Jing-Yao, Sun Zhihu, Zheng Xusheng, Jiao Long, Jiang Hai-Long
Hefei National Research Center for Physical Sciences at the Microscale, Department of Chemistry, University of Science and Technology of China, Hefei, Anhui 230026, People's Republic of China.
Key Laboratory of Precision and Intelligent Chemistry, University of Science and Technology of China, Hefei, Anhui 230026, People's Republic of China.
Proc Natl Acad Sci U S A. 2025 Apr 15;122(15):e2419434122. doi: 10.1073/pnas.2419434122. Epub 2025 Apr 10.
The microenvironment around catalytic sites plays crucial roles in enzymatic catalysis while its precise control in heterogeneous catalysts remains challenging. Herein, the coordinatively unsaturated metal nodes of Hf-based metal-organic framework nanosheets are simultaneously codecorated with catalytically active Co(salen) units and adjacent pyridyl-substituted alkyl carboxylic acids via a post modification route. By varying pyridyl-substituted alkyl carboxylic acids, the spatial positioning of the N atom in pyridine group relative to adjacent Co(salen) can be precisely controlled. Notably, the 3-(pyridin-4-yl)propionic acid, with -position pyridine N atom, maximally improves the electrocatalytic CO reduction performance of Co(salen) unit, far superior to other counterparts. Mechanism investigations reveal that the pyridine unit of 3-(pyridin-4-yl)propionic acid is optimally positioned relative to Co(salen) and undergoes in situ reduction to pyridinyl radical under working potentials. This greatly facilitates the stabilization of *COOH intermediate via hydrogen-bonding interaction, lowering the formation energy barrier of *COOH and therefore boosting CO electroreduction.
催化位点周围的微环境在酶催化中起着关键作用，而在多相催化剂中对其进行精确控制仍然具有挑战性。在此，通过后修饰路线，基于铪的金属有机框架纳米片的配位不饱和金属节点同时被具有催化活性的Co(salen)单元和相邻的吡啶基取代的烷基羧酸共修饰。通过改变吡啶基取代的烷基羧酸，可以精确控制吡啶基团中N原子相对于相邻Co(salen)的空间位置。值得注意的是，具有β-位吡啶N原子的3-(吡啶-4-基)丙酸最大程度地提高了Co(salen)单元的电催化CO还原性能，远优于其他同类物质。机理研究表明，3-(吡啶-4-基)丙酸的吡啶单元相对于Co(salen)处于最佳位置，并在工作电位下原位还原为吡啶基自由基。这极大地促进了通过氢键相互作用对COOH中间体的稳定作用，降低了COOH的形成能垒，从而促进了CO电还原。
