Polydopamine Coatings with Nanopores for Versatile Molecular Separation.

The demand for highly efficient and multifunctional membranes in various separation processes is increasing. Recently, mussel-inspired polydopamine (PDA) has provided a promising way to meet these requirements because of its surface-adhesive property and film-forming ability. However, traditional PDA coatings usually suffer from the disadvantages of nonuniformity, incompactness, and instability, leading to poor molecular separation and service performance. Herein, uniform, compact, and robust PDA coatings were fabricated on an ultrafiltration substrate via a reasonable screening of oxidants for the oxidized self-polymerization of dopamine. The as-prepared PDA coatings were nanoporous (0.56 ± 0.04 and 0.93 ± 0.04 nm) with a thickness of ∼75 nm, which endows the composite membranes with a high solute rejection and solvent permeability during molecular separation. They are useful in organic solvent nanofiltration because of their superior structural stability. Moreover, the composite membranes can be used for recycling the nanometer catalyst from organic solvents for the first time, which has significantly broadened the potential applications of these mussel-inspired coatings for versatile separation processes.