Two-dimensional fractal nanocrystals templating for substantial performance enhancement of polyamide nanofiltration membrane

Significance Fractal structures and phenomena have existed in nature for hundreds of millions of years. Developing their practical applications in material design is of fundamental importance, but this goal has not yet been reached. In this work, NaCl crystals with a fractal structure are formed between the polyamide active layer and the support during an interfacial polymerization process. The branching of fractal NaCl nanocrystals creates numerous tiny interworking water channels that enable water transport, maximizing the effective permeating area of the polyamide nanofiltration (NF) membrane. The fractal NaCl nanocrystals–templated polyamide NF membrane exhibits an improved desalination performance with a three to four times increase in permeance. Applying fractal structure successfully to the design of artificial materials improves performance.