Ultrathin nanosheets show great promise in photocatalytic technology, due to short path for electron transfer and large surface for reactant adsorption. However, there is no report that ultrathin nanosheets photocatalyst has been used to degrade carbamazepine (CBZ) in aquatic environment. This paper aimed at fabricating ultrathin BiOCl nanosheets to improve the photocatalytic degradation efficiency of CBZ. Herein, tetrabutylammonium hydroxide (TBAOH) was firstly applied to synthesize ultrathin BiOCl nanosheets (BiOCl-T) by a simple hydrolysis route in water at ambient conditions. TBAOH could act as a structure-directing agent, determining the structure and property of BiOCl-T. Assisted by TBAOH, BiOCl-T exhibited ultrathin nanosheets structure with preferential exposed (1 1 0) face. PL, photocurrent density, and EIS Nyquist plots demonstrated the enhanced charge separation efficiency in BiOCl-T. Furthermore, BiOCl-T displayed large pore size and specific surface area. Thus, BiOCl-T showed high photocatalytic activity toward CBZ degradation under simulated sunlight. Upon 30 min irradiation, the degradation efficiency of CBZ was 91.1% with fast degradation kinetics, which is 2.46 times higher than ordinary BiOCl. Active species of h(+), center dot O-2, and center dot OH contributed to CBZ degradation reaction. The obtained result provides a novel viewpoint to fabricate ultrathin nanosheets and broadening their application in the degradation of recalcitrant pharmaceuticals. (C) 2020 Elsevier Inc. All rights reserved.