Synergistic effects of boron nitride quantum dots and reduced ultrathin g-C3N4: dual-channel carrier transfer and band structure regulation boost the photodegradation of fluoroquinolone

[Display omitted] •A novel BNRU photocatalyst was synthesized via a facile method.•Band structure optimization and dual-channel carrier transfers could be achieved in the BNRU.•BNRU possessed enhanced oxidation capacities and photocarriers production-separation efficiencies.•BNRU exhibited outstanding photocatalytic activities under visible and natural solar light. The synergistic enhancement of photocarriers production-separation and oxidation capacities of g-C3N4 to improve its catalytic performance for environmental remediation remains a challenge. Herein, we prepared a novel boron nitride quantum dots (BNQDs)-decorated reduced ultrathin g-C3N4 (BNRU) composite, toward achieving the above objective through the synergistic effects of defect engineering and BNQDs loading. By introducing the defects (nitrogen vacancies (NVs) and cyano group), the optimized band structure absorbed more photons and provided a stronger oxidation driving force (+2.15 V). Meanwhile, NVs and BNQDs formed distinct electron-hole transfer channels to facilitate photocarriers separation. Compared with ultrathin g-C3N4, the optimal 2BNRU showed a 1.7-folds higher carrier density, and the photocurrent density increased from 1.33 to 9.31 μA/cm2 under visible light exposure. Electron spin resonance and molecular probe spectroscopy results revealed that these enhanced properties endowed 2BNRU with the superior capacity to generate free radicals. The 2BNRU completely removed 10 mg/L of norfloxacin molecules at a kinetic rate of 0.3744 min−1, and the mineralization rate attained 46.9 % under 30 min of visible light irradiation. Meanwhile, the 2BNRU system exhibited promising feasibility for a simulated water treatment process.