Atomically isolated Sb(CN)₃ on sp²-c-COFs with balanced hydrophilic and oleophilic sites for photocatalytic C-H activation.

Abstract

Activation of carbon-hydrogen (C-H) bonds is of utmost importance for the synthesis of vital molecules. Toward achieving efficient photocatalytic C-H activation, our investigation revealed that incorporating hydrophilic C≡N-Sb(CN)₃ sites into hydrophobic sp² carbon-conjugated covalent organic frameworks (sp²-c-COFs) had a dual effect: It simultaneously enhanced charge separation and improved generation of polar reactive oxygen species. Detailed spectroscopy measurements and simulations showed that C≡N-Sb(CN)₃ primarily functioned as water capture sites, which were not directly involved in photocatalysis. However, the potent interaction between water molecules and the Sb(CN)₃-modified framework notably enhanced charge dynamics in hydrophobic sp²-c-COFs. The reactive species ·O₂^- and ·OH (ad) subsequently combined with benzyl radical, leading to the formation of benzaldehyde, benzyl alcohol, and lastly benzyl benzoate. Notably, the Sb(CN)₃-modified sp²-c-COFs exhibited a 54-fold improvement in reaction rate as compared to pristine sp²-c-COFs, which achieved a remarkable 68% conversion rate for toluene and an 80% selectivity for benzyl benzoate.