Anthraquinone‐Based Donor–Acceptor Covalent Organic Frameworks with Thiazole Linkages to Enhance Direct Hydrogen Atom Transfer and Charge Separation in Photocatalytic Oxidation of C(sp ³ )─H Bonds

Abstract

Abstract The design of efficient covalent organic frameworks (COFs) as photocatalysts for C(sp 3 )─H bond oxidation under green and mild conditions is highly desirable. Herein, TpAQ‐TZ COF and TpAR‐TZ COF, featuring thiazole linkages, were synthesized by combining 1,3,5‐tricarboxylcarboxaldehyde (Tp), sulfur (S 8 ), and direct hydrogen atom transfer ( d ‐HAT) components (2,6‐diaminoanthraquinone, AQ; 2,6‐diaminoanthrone, AR). The TpAQ‐TZ COF demonstrates impressive photocatalytic activity, achieving a 93% yield for phthalan oxidation under heterogeneous conditions—a rare example of photocatalytic C(sp 3 )─H bond oxidation in water under ambient conditions. Theoretical calculations reveal enhanced hydrogen atom abstraction capability coming from the increased number of d ‐HAT catalytic sites. Moreover, BdAQ‐TZ COF and HbAQ‐TZ COF were prepared by replacing Tp with 2,4‐dihydroxy‐1,3,5‐triformylbenzene (Bd) or 2‐hydroxy‐1,3,5‐triformylbenzene (Hb), respectively. Dipole moment calculations and femtosecond transient absorption spectroscopy show that the increased number of hydroxyl groups on the benzene‐1,3,5‐tricarbaldehyde monomer improves the charge separation efficiency within the three COFs, thereby accounting for the enhanced photocatalytic activity of TpAQ‐TZ COF. This work opens up new opportunities for designing highly active photocatalysts by using the synergistic effects of d ‐HAT, O 2 •− , and 1 O 2 within anthraquinone‐based donor–acceptor COF platforms, offering a sustainable route for the oxidation of C(sp 3 )─H bonds under environmentally friendly conditions.