In this paper, a novel 0D/2D heterojunction photocatalyst based on MoS2 QDs/ZnO nanosheets was successfully constructed by a simple two-step process, and its photocatalytic behavior for organic dyes (RhB) degradation and gaseous heavy metals (Hg) removal under ultraviolet light were studied. For the optimum 5% MoS2/ZnO photocatalyst, 95% of RhB could be removed in 50 min, and 99.8% of the gaseous mercury could be removed in 60 min. Besides, MoS2 QDs/ZnO nanosheets also exhibited excellent photocatalytic durability. The constructed 0D/2D heterojunctions could efficiently improve the separation efficiency and charge transfer of photogenerated carriers, thus improving the photocatalytic activity. Therefore, this strategy provided a new way to design bifunctional 0D/2D heterojunction photocatalysts for water treatment and air pollution. (C) 2020 Elsevier Inc. All rights reserved.