Liu Guochao, Lin Min, Xing Yali, Cheng Shuqi, Wang Han, Li Daohao, Long Xiaojing, Fang Qianrong
State Key Laboratory of Bio-fibers and Eco-textiles, Institute of Marine Biobased Materials, College of Materials Science and Engineering, Qingdao University, Qingdao, 266071, P.R. China.
State Key Laboratory of Inorganic Synthesis and Preparative Chemistry, Jilin University, Changchun, 130012, P.R. China.
Angew Chem Int Ed Engl. 2025 Jun 10;64(24):e202500945. doi: 10.1002/anie.202500945. Epub 2025 Apr 14.
Oligoethers with various numbers of ethylene oxide (EO) units, known for their flexibility, electronegativity, and hydrophilicity, can be leveraged to construct complex molecular architectures with broad applicability. In this study, we present the synthesis of two-dimensional (2D) covalent organic frameworks (COFs) incorporating oligoethers with EO segments of varying lengths (2D-COF-EOs) to explore the role of EO units in modulating the two-electron (2e) oxygen reduction reaction (ORR) pathway for electrocatalytic hydrogen peroxide (HO) production. By embedding hydrophilic EO side chains into the hydrophobic frameworks, intermolecular interactions are promoted through hydrogen bonding, leading to the self-assembly and spatial aggregation of these side chains. The high crystallinity of the COFs facilitates orderly stacking of the skeleton, creating hydrophilic nanoscale transport channels that enhance ORR kinetics. Among the synthesized COFs, 2D-COF-EO, which contains one EO group, exhibits a remarkable HO production rate of 5820 mmol g h and a 2e ORR selectivity of 89.2%. Theoretical calculations and in situ electrocatalytic experiments reveal that the elongation of the EO units significantly alters the electronic structure of carbon atoms adjacent to oxygen atoms, lowering the energy barriers associated with the formation of OOH* intermediates and thus promoting the 2e ORR pathway. This work offers valuable insights into optimizing COFs with different EO units for efficient 2e ORR-based electrocatalytic processes.
具有不同数量环氧乙烷（EO）单元的低聚醚，以其柔韧性、电负性和亲水性而闻名，可用于构建具有广泛适用性的复杂分子结构。在本研究中，我们展示了二维（2D）共价有机框架（COF）的合成，该框架包含具有不同长度EO链段的低聚醚（2D-COF-EO），以探索EO单元在调节双电子（2e）氧还原反应（ORR）途径以电催化生产过氧化氢（HO）中的作用。通过将亲水性EO侧链嵌入疏水性框架中，分子间相互作用通过氢键得到促进，导致这些侧链的自组装和空间聚集。COF的高结晶度有利于骨架的有序堆积，形成亲水性纳米级传输通道，从而增强ORR动力学。在合成的COF中，含有一个EO基团的2D-COF-EO表现出显著的HO生成速率，为5820 mmol g h，2e ORR选择性为89.2%。理论计算和原位电催化实验表明，EO单元的延长显著改变了与氧原子相邻的碳原子的电子结构，降低了与形成OOH*中间体相关的能垒，从而促进了2e ORR途径。这项工作为优化具有不同EO单元的COF以实现基于2e ORR的高效电催化过程提供了有价值的见解。
