Designing COF Photocatalyst Based on H 2 O Receptors for Enhanced Methyl(Phenyl)Sulfane Oxidation Under Aqueous Solvents

ABSTRACT Developing efficient photocatalytic systems in water remains challenging due to poor compatibility of conventional photocatalysts. Herein, we report an anthrone‐functionalized covalent organic framework (DAAQ‐COF) that acts as an intrinsic water molecular receptor, enabling highly efficient photocatalytic oxidation of methyl(phenyl)sulfane under aqueous conditions. Unlike its structural analogue lacking the anthrone moiety (ATDA‐COF), DAAQ‐COF exhibits a pronounced electronic response upon hydration: the bandgap narrows significantly from 2.44 to 1.74 eV, and photoluminescence is substantially quenched, indicating enhanced charge separation—findings consistently supported by spectroscopic and computational analyses. As a result, DAAQ‐COF achieves a 98% yield of the corresponding sulfoxide within 4 h under blue LED irradiation in an EtOH/H 2 O (1:2) solvent system, markedly outperforming ATDA‐COF (60% yield under identical conditions). Mechanistic studies attribute this superior performance to the anthrone unit, which accelerates electron delocalization and intramolecular charge transfer, thereby promoting the adsorption and diffusion of both the substrate and molecular oxygen. Consequently, the reaction kinetics are significantly improved, enabling near‐quantitative conversion with excellent chemoselectivity. By harnessing water as both a medium and an electronic modulator, this work establishes a design strategy that transforms water into an integral component of catalytic function for sustainable photocatalysis.