Synergistic Regulation of Charge Delocalization and Built-In Electric Field in COF-Supported Single-Atom Catalysts for Enhanced H₂O₂ Photosynthesis.

Abstract

Photocatalytic production of H₂O₂ from O₂ is attractive yet often self-limiting because oxygenated intermediates persist on catalyst surfaces triggering O─O bond cleavage and H₂O₂ decomposition. Herein, we demonstrate that this bottleneck can be mitigated by coordination-microenvironment control coupling an enhanced built-in electric field with regulated charge delocalization. A sulfonated covalent organic framework (TpPa -SO₃H-COF) was used as the support, and single Ni atoms were anchored at two distinct sites to form two atomically dispersed catalysts with the same metal species but markedly different local fields and coordination environments. Theoretical calculations and spectroscopic characterizations indicate that N coordination induces electron density redistribution, thereby enabling charge delocalization at the Ni center and further weakening *OOH adsorption. Meanwhile, a strengthened built-in electric field further enhances photogenerated electron-hole separation. As a result, the N-coordinated site (N₁─Ni─O₂) achieves an enhanced H₂O₂ production rate of 7189.52 µmol g^-1·h^-1 under sacrificial-agent-free conditions. This work identifies coordination-driven regulation of the built-in electric field and charge delocalization as an effective strategy for photocatalytic H₂O₂ synthesis, providing valuable insights for the rational design of efficient photocatalysts.