Grafting anthraquinone on ultrathin C₃N₄ for selective toluene photooxidation

Anthraquinone (AQ), an effective hydrogen atom transfer catalyst, is limited in photocatalytic applications due to its dimerization. In this study, a simple 3-(3-(dimethylamino) propyl)-1-ethylcarbodiimide hydrochloride/N-hydroxysuccinimide (EDC/HNS) assisted linking strategy was developed to covalently graft AQ–COOH onto C₃N₄ (CN). Using this method, we successfully synthesized amide-bonded CN–AQ ultrathin nanosheets. The amide covalent bond formed between C₃N₄ and AQ facilitates efficient electron migration from C₃N₄ to AQ. As a result, charge carrier recombination is prevented and the hydrogen atom transfer capacity of AQ is enhanced. The CN–AQ photocatalyst exhibits high activity and selectivity with a toluene conversion rate of 10274 (mol g⁻¹ h⁻¹ and 85% selectivity for benzaldehyde, which is 31 times and 1.7 times higher than those of pristine C₃N₄ and AQ–COOH, respectively. Owing to the strong covalent bond in CN–AQ composite, the stability of AQ–COOH was greatly enhanced. This approach provides a new pathway to improve catalytic efficiency and solve the dimerization problem of AQ.