Unveiling the Dynamic Evolution of Single-Atom Co Sites in Covalent Triazine Frameworks for Enhanced H<sub>2</sub>O<sub>2</sub> Photosynthesis
Chao Zhu, Yanchi Yao, Qile Fang, Shuang Song, Baoliang Chen, Yi Shen
Abstract
Unraveling the structural evolution and mechanism of active sites in single-atom catalysts (SACs) during H 2 O 2 production under operational conditions remains challenging due to the transient and elusive nature of the underlying reaction processes. Herein, we employ operando X-ray absorption spectroscopy and ab initio molecular dynamics simulations to unveil the dynamic reconstruction behavior of the Co single atom-loaded covalent triazine framework (Co SA /Py-CTF) during photocatalytic H 2 O 2 production. The unique Py-CTF substrate provides reasonable structural flexibility to the single atom Co site. Under light irradiation and O 2 adsorption, single Co atoms are dynamically released from the Py-CTF substrate and then form transient atom-pairs with neighboring Co atoms, serving as the authentic active site. The dynamic shuttling of Co subnanometer domains between single-atoms and atom-pairs facilitates the transition of the O 2 adsorption configurations from Pauling type to Yeager type, resulting in a record photocatalytic H 2 O 2 yield (2898.3 μmol·h –1 ·g –1 ). These findings provide insightful observations into the dynamic photochemical behavior of SACs and present an fresh paradigm for the design of intelligent “adaptive catalysts”.