Schiff-Base-Bridged Cyclodextrin-Modified Carbon Nitride for Efficient Sacrificial-Agent-Free Photocatalytic H2O2 Production

Abstract

Solar-driven photocatalytic H2O2 production provides a sustainable alternative to the energy-intensive anthraquinone process. However, graphitic carbon nitride (CN) suffers from rapid charge recombination and inefficient activation of molecular oxygen, leading to limited H2O2 production. Herein, we report a Schiff-base-interface-engineered organic-polymer-functionalized CN (ACD-DAMP-CN), synthesized via hydrothermal condensation of oxidized β-cyclodextrin (ACD), 4,6-diamino-2-mercaptopyrimidine (DAMP), and surface amino groups on CN. The covalently coupled Schiff-base interface regulates the electronic structure of CN, promotes directional interfacial charge transfer, and facilitates the selective two-electron oxygen reduction reaction (2e– ORR) toward H2O2 generation. Consequently, ACD-DAMP-CN achieves an H2O2 evolution rate of 600 μmol g–1 h–1 under simulated sunlight irradiation in pure water without oxygen aeration, which is 18.75 times higher than that of pristine CN. Experimental characterizations combined with DFT calculations reveal that electron redistribution across the Schiff-base bridge enhances charge separation by transferring electron density from the electron-rich DAMP moieties to the CN framework, thereby promoting efficient 2e– ORR. Moreover, the catalyst exhibits excellent stability over five consecutive cycles and maintains high activity over a wide pH range (2–12). The in situ-generated H2O2 further enables efficient photo-Fenton degradation of ciprofloxacin, demonstrating a feasible strategy for integrating selective photocatalytic H2O2 production with solar-driven environmental remediation.