Single active-site catalysts constructed with nonpolar-bond linked covalent organic frameworks for oxygen reduction reaction  

非极性键连接的共价有机框架用于构建氧还原反应单活性位点催化剂

作　　者：Fancheng Meng Xuewen Li Qizheng An Shuai Yang Zixing Zhang Qing Xu Bai Xue Xin Jin Fan Zhang 孟凡成;李雪文;安奇正;杨帅;张子星;徐庆;薛白;金鑫;张帆

机构地区：[1]School of Chemistry and Chemical Engineering,State Key Laboratory of Meal Matrix Composites,Shanghai jiao Tong University,Shanghai 200240,China [2]CAS Key Laboratory of Low-Carbon Conversion Science and Engineering,Shanghai Advanced Research Institute(SARI),Chinese Academy of Sciences(CAS),Shanghai 201210,China [3]School of Chemical Engineering,University of Chinese Academy of Sciences,Beijing 100049,China [4]National Synchrotron Radiation Laboratory,University of Science and Technology of China,Hefei 230029,China

出　　处：《Science China Materials》2025年第4期1138-1144,共7页中国科学(材料科学)(英文版)

基　　金：financially supported by the Science and Technology Commission of Shanghai Municipality(20JC1414900);the National Natural Science Foundation of China(22271188,22075178,22005189);the China Postdoctoral Science Foundation(2023M742244)。

摘　　要：Covalent organic frameworks(COFs)with polar linkages have been employed as metal-free catalysts for the oxygen reduction reaction(ORR).However,it is still a big challenge to precisely design or locate the catalytic sites for such kinds of COFs because their polar linkages always make some catalytic activity.In addition,the polar linkages are facile to bind with O_(2) and oxygen-contained intermediates in the catalytic process,severely weakening the long-term stability of these COFs.In this work,we demonstrated the single metalfree catalytic sites based on the pyridine-cored COFs with nonpolar linkages(C=C bonds)to catalyze the ORR.The nonpolar linkages excluded their potential roles as catalytic sites and also circumvented the possible decomposition in the process of catalysis.By modulating the pyridine N with positive charges,the catalytic performance can be previously improved,because of the enhanced Lewis acidity of the carbon atoms next to the pyridine N,and thus favorable for the electrons transfer to the catalytic sites.The newly-synthesized charged COF showed high activity of a half-wave potential of 0.74 V with a mass activity of 4.34 A g^(-1),which was 50 mV more positive and 1.63 times higher than those of the neutral COF.And the nonpolar linkages made the COFs display better long-term stability than other metal-free COFs.The theoretical calculation revealed that the ionization of pyridine promoted the formation of the intermediate OOH*,and thus improved the catalytic activity.This work gives us a new insight into designing single sites based on COFs.极性键连接的共价有机骨架(COFs)已经广泛用作氧还原反应(ORR)的非金属催化剂.然而,由于这类COFs中的极性连接键通常具有一定的催化活性,因此精确设计或定位其催化位点仍然是一个很大的挑战.此外,极性连接键在催化过程中容易与O_(2)和含氧中间体结合,严重削弱了这些COFs的长期稳定性.在这项工作中,我们阐明了基于非极性键(C=C键)连接的吡啶核COFs拥有非金属单催化位点结构,并用于催化ORR.非极性键排除了作为潜在催化位点作用,也避免了催化过程中可能发生分解.由于吡啶N可增强相邻碳原子路易斯酸性,有利于电子转移到催化位点,因而,通过带正电荷调制吡啶N,可以预活化催化性能.所制备的带正电荷COF骨架具有高催化活性,其半波电位为0.74 V,质量活性为4.34 A g^(-1),比中性COF高出50 mV,是其1.63倍.此外,非极性键的存在使其表现出较好的长期稳定性.理论计算表明,季铵化吡啶促进了中间体OOH*的生成,从而提高了催化活性.这项工作使我们对基于COFs的单一催化位点设计有了新的认识.

关 键 词：covalent organic frameworks charging-tuned nonpolar linkage Lewis acidity oxygen reduction reaction 

分 类 号：O643.36[理学—物理化学]