Solar steam generation through photothermal conversion and heat localization is an emerging technology that can potentially alleviate shortages of clean water. As a two-dimensional transition-metal dichalcogenide, molybdenum disulfide (MoS2) has been employed for harvesting solar energy in hydrogen gas production, disinfection, and solar cells. Here, for the first time, we demonstrate that chemically exfoliated (ce) MoS2can be a highly efficient, scalable, and environmentally benign (low toxicity) photothermal material for solar evaporators to create fresh water. Notably, the phase transition of MoS2from 2H (trigonal prismatic coordination) to 1T (octahedral coordination) during the exfoliation process enhances the light absorption of the ce-MoS2, generating heat more effectively. Owing to the efficient photothermal conversion of ce-MoS2nanosheets and heat localization from using bacterial nanocellulose foam as support, high solar evaporation efficiencies of ~ 76% and ~ 81% are achieved under 0.76 kW/m2and 5.35 kW/m2light intensities, respectively. In addition, the cytotoxicity of ce-MoS2nanosheets was lower than that of graphene oxide (GO) nanosheets with a similar size, a commonly suggested material for solar steam generation, which can alleviate the potential environmental risk. These findings not only establish ce-MoS2as a highly attractive material for solar steam generation, but also broaden the uses of ce-MoS2to include solar harvesting applications.