The identification of new practical routes through rational design of membranes is mandatory to enhance the quality of minerals recovered from seawater and/or brine using advanced technologies based on membrane engineering. Here, we demonstrate that the inclusion of Bi2Se3 fillers in polyvinylidene membranes assists the crystal-growth for NaCl, leading to a higher uniformity of the crystal size when membrane crystallization is implemented. The vacancies formed throughout the Bi2Se3 crystals’ surfaces are suggested to withdraw water molecules from ion cores, stimulating quicker ion–ion interaction and aggregation with time. This discovery is expected to open the way towards the exploitation of this class of materials in advanced membrane separations.