• • BiOBr achieved a peak NO removal rate of 58% under optimized conditions (light source distance 15 cm, NO flow 15 mL/min, oxygen present), demonstrating its practical potential for air purification.
• • The degradation rate constant for BiOBr was 11×10⁻⁴ min⁻¹, significantly outperforming BiOCl and BiOI, indicating superior photocatalytic kinetics.
• • BiOBr's flower-like nanomicrosphere morphology, composed of nanosheets, yields a larger specific surface area and enhanced visible light absorption, directly correlating with its higher activity.
• • The bandgap of BiOX series decreases with increasing halogen atomic number, yet BiOBr's moderate bandgap provides the most balanced visible light absorption, highlighting the importance of band structure engineering.