Constructing high-density active sites on hollow covalent organic polymers for efficient oxygen electrocatalysis.

Creating efficient catalytic sites on covalent organic polymers (COPs) is a promising approach for green energy conversion and industrial catalysis. Although the post-synthetic modification of COPs has made progress in constructing single-atom sites and metal nanoparticles, this method remains limited in terms of the types, quantities, and overall performance of the constructing sites. To address these limitations, we develop a template-source construction strategy for catalytic site establishment. This strategy successfully yields hollow COPs with a high content of Co-O active species (H-COP-Co), demonstrating high activity as oxygen electrocatalysts. Comparing to traditional post-synthetically modified COPs with single Co sites (S-COP-Co), H-COP-Co demonstrates an increase in active metal content, from 2.96% to 56.86%, with enhanced catalytic activity for oxygen evolution reaction (OER). Unlike single Co sites that operate via the adsorbate evolution mechanism (AEM), comprehensive spectroscopic characterization and theoretical calculations reveal that the initial and reconstructed Co oxide nanoparticles in COPs operate via the oxide path mechanism, serving as the origin of the superior OER performance. These findings provide valuable insights into the design of multifunctional composite COP materials, underscoring the importance of intrinsically structural designing and modulating reaction mechanisms to enhance energy conversion efficiency.