Synergistic Dual-Site Regulation in a Tailored Imine-COF for Enhanced Hydrogen Peroxide Photosynthesis.

Abstract

Covalent organic frameworks (COFs) emerge as promising candidates for the photocatalytic production of hydrogen peroxide (H2O2). However, precise modulation of the chemical environment of active sites in COFs remains a significant challenge. Based on a molecular engineering strategy, this study focuses on hierarchical regulation of nitrogen coordination environments for efficient photocatalytic H2O2 production through the 2e- ORR. Intrinsic nitrogen configurations (triazine vs. pyridine) are first tailored to construct two types of COFs. The pyridyl-imine TAPT-BTPA (4) optimizes charge carrier separation and extends visible-light absorption, leading to an enhanced H2O2 production rate of 8.12 mmol g-1 h-1 in aqueous solution containing isopropanol as a sacrificial agent under an O2 atmosphere. Main-group metals (In, Sn, and Sb) are then anchored at the pyridine-imine sites to modulate local electron density further and steer reaction pathways. Structural characterization and activity tests reveal that Sb-coordinated TAPT-BTPA-Sb (10) induces a unique synergistic effect, redirecting the ORR toward a more favorable stepwise 1e- route. This significant pathway regulation ultimately boosts the H2O2 production rate to 15.3 mmol g-1 h-1 under the same conditions. This work clarifies the decisive role of coordination environment engineering and establishes a molecular-level design paradigm for advanced H2O2 synthesis photocatalysts.

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