Removing salt is only one step in creating clean water from ocean or brackish water. Toxic compounds, from metals to human-made carcinogens, must be removed by subsequent processing. Chemists have invented a technique to remove salt and toxic ions in one step. They create porous nanoparticles, PAFs, with added functional groups that selectively absorb ionic compounds, like metals, or neutral species, like boron, then add them to the polymer membranes used in electrodialysis.