Metal-free 2D/2D heterojunction of covalent triazine-based frameworks/graphitic carbon nitride with enhanced interfacial charge separation for highly efficient photocatalytic elimination of antibiotic pollutants

Abstract

A novel polymer-based 2D/2D heterojunction photocatalysts of covalent triazine-based frameworks/graphitic carbon nitride nanosheets (CTFNS/CNNS) heterojunction are successfully obtained by an electrostatic self-assembly method using amine-functionalized CNNS and carboxyl-rich CTFNS. Such large contact surface and appropriate interfacial contact between CNNS and CTFNS plays a critical role in transfer and separation of charge-carriers. The resulting CTFNS/CNNS heterojunction showed significantly enhanced photocatalytic activity under the irradiation of simulated solar light, which could decompose 10 ppm sulfamethazine (SMT) within 180 min with a high degradation efficiency of 95.8 %. Chloride ions can greatly promote the photocatalytic degradation of SMT due to the production of more radical species. O2− is the dominant active species for SMT decomposition over CTFNS/CNNS heterojunction. Moreover, the degradation intermediates of SMT were identified using high performance liquid chromatography-mass spectrometer and the degradation pathway was proposed. This study provides a new insight into the design of 2D/2D heterojunctions using carbon-based nanomaterials, which exhibits great potential in the degradation of sulfonamide antibiotics in wastewaters.