<p>2-Mercaptobenzothiazole (2-MBT) is a prevalent organic pollutant in the environment that poses significant challenges for complete removal using conventional water treatment methods. In this study, we successfully synthesized Bi₃O₄Br/MMT composites by incorporating the clay mineral montmorillonite (MMT), which effectively addresses the issues of low specific surface area and poor adsorption performance commonly observed in traditional Bi₃O₄Br materials. Furthermore, the aluminum species in MMT facilitate the transfer of photogenerated electrons from Bi₃O₄Br to MMT, thereby inhibiting the recombination of electron–hole pairs and enhancing photocatalytic performance. The photocatalytic properties of the photocatalyst were appraised using 2-MBT as the target contaminant. The Bi₃O₄Br/MMT composites demonstrated a remarkable degradation efficiency of nearly 90% for 2-MBT within just 3&#xa0;min of visible-light irradiation, surpassing 99% after 7&#xa0;min, along with exceptional cycling stability and structural integrity. Quenching experiments and electron paramagnetic resonance (EPR) analysis identified superoxide radicals (·O₂⁻), holes (h⁺), and electrons (e⁻) as the primary reactive species driving the photocatalytic degradation of 2-MBT. This work provides a promising strategy for the development of environmentally friendly catalytic systems for the efficient degradation of 2-MBT in water.</p> Graphical abstract <p></p>