A pyridine-woven covalent organic framework facilitating the immobilization of Co single atoms towards efficient photocatalytic H2 evolution

Abstract

Solar-driven hydrogen evolution from water splitting provides an ideal protocol for alleviating the global energy crisis and environmental issues. However, the efficiency of photocatalytic hydrogen evolution is often limited by poor light-absorption ability, sluggish electron–hole kinetics, and ineffective charge transfer. Herein, a pyridine-contained covalent triazine framework was delicately designed to facilitate single-atom Co immobilization (Co₁-PCTF), exhibiting an impressive hydrogen evolution rate of 2562.4 μmol g⁻¹ h⁻¹, which is much higher than that of the pristine CTF. It has been experimentally and theoretically demonstrated that the introduction of the pyridine ring significantly enhanced the π-conjugation degree, optimizing the band structure and extending the visible-light absorption. The highly dispersed Co atoms show notable electron-rich properties, promoting charge separation and offering abundant active sites for H⁺ reduction. Additionally, the robust Co–N bridge with a large potential difference creates a built-in electronic field for efficient directional transfer from the organic substrate to the Co site. This study provides novel insights into the rational design of CTF-based advanced photocatalysts with high activity and durability.