Fig. 1: Schematic illustration of nano-confined crystallizations in polymer membranes for water-solute selectivity.

Multivalent H-bond interactions can manipulate controllable and organized crystallization at the air/water interface under nanoconfinement. This arrangement offers dual benefits: refining the distribution of pore sizes for ultra-selectivity and boosting the free volume for enhanced water permeation. Compared to nano-confined regular crystallization (NRC) membranes, nano-confined controllable crystallization (NCC) membranes exhibit a greater fractional free volume and a more refined pore size distribution, thus promoting water-salt selectivity.