Solar steam generation has been considered as an effective way to solve the shortage of freshwater resources. In this paper, we have designed an interfacial evaporation device for efficient solar steam generation based on near infrared (NIR)-absorbing lanthanum hexaboride (LaB6) nanoparticles and melamine sponge (MS) as the skeleton. LaB6 nanoparticles as a photothermal conversion material can absorb the NIR light and convert it into heat. Due to the porous 3D network and better hydrophilicity of MS, it can act as a substrate to support the LaB6 dispersed on the surface and transport the water by the capillary force. The evaporation rate of 1.13 kg m(-2) h(-1) and photothermal conversion efficiency of 60.7% under 1 kW m(-2) solar illumination were achieved. Moreover, LaB6-MS photothermal conversion device (LaB6-MS PTCD), with excellent chemical stability could purify different water sources such as simulated seawater, strong acid, strong alkaline, and dyed methylene blue solution, exhibiting promising application in highly efficient solar energy-driven seawater desalination and wastewater purification.