Covalently coupled g-C3N4@Zn/Eu-MOF heterojunction for photocatalytic degradation and ratiometric fluorescence detection of ofloxacin

A heterojunction with g-C 3 N 4 @Zn/Eu-MOF covalent interface was synthesized. • g-CN@MOF can be used for photocatalytic degradation and fluorescence detection of ofloxacin. • Efficient removal of ofloxacin in milk by g-CN@MOF foam. • g-CN@MOF can detect ofloxacin residues in milk through smartphone-assisted color recognition. Ofloxacin (OFL) is widely used in medicine and animal husbandry, and its residues in milk raise substantial food-safety concerns. Herein, a dual-functional covalently coupled g-C 3 N 4 @Zn/Eu-MOF composite (g-CN@MOF) was constructed through a one-pot hydrothermal route. FTIR and XPS analyses indicated the formation of C N C O linkages between g-C 3 N 4 and the MOF, yielding an interfacially coupled type-II heterojunction that promoted charge separation. The optimized g-CN@MOF-30 achieved 69.21% removal of 10 mg L −1 OFL within 120 min under visible light, with •O 2 − and •OH identified as the dominant reactive species. Meanwhile, the fluorescence intensity ratio F 440 /F 595 showed a linear response to OFL over the range of 0–100 μM, affording a detection limit of 0.011 μM through an IFE-dominated ratiometric sensing mechanism. After immobilization in sodium alginate foam, the composite exhibited convenient recyclability and enabled OFL removal from pretreated milk samples, while smartphone-based RGB analysis provided rapid visual semi-quantification with recoveries ranging from 100.3% to 109.9%. Download: Download high-res image (269KB) Download: Download full-size image