One-step purification and desalination: The purification of water for drinking purposes can require multiple filtration steps and technologies to remove contaminants such as salts and heavy metals. Some contaminants could have value if recovered, but these are often discharged in the waste streams. Uliana et al. describe a general approach for the fabrication of robust, tunable, adsorptive membranes through the incorporation of porous aromatic framework (PAF) nanoparticles into ion exchange membranes such as those made from sulfonated polymers. Salts are removed using a series of cation and anion exchange membranes, and the PAF particles can be selected to capture specific target ions, such as those of copper, mercury, or iron. This allows for simultaneous desalination and decontamination of the water. Science , this issue p. 296