Fabrication of multilayer heterostructure organic-inorganic composite membranes by soft spray technique for dye separation

Composite nanofiltration membranes have significant potential for advanced membrane separations. However, the challenge of balancing membrane selectivity and permeability remains substantial. Herein, we report a novel approach to fabricating multilayer heterogeneous organic-inorganic composite membranes (Cu-3(PO4)(2)/SA/PmPD) using a soft spray technique assisted by the miscible interface. Based on the superiority of the soft spray technique and the ionic crosslinking properties of sodium alginate (SA), two-dimensional (2D) interleaving Cu-3(PO4)(2) nanosheets and poly(m-phenylenediamine) (PmPD) membranes were sequentially grown in situ on the surface of SA through a two-step process. Each component plays a crucial role in constructing and enhancing the separation performance of Cu-3(PO4)(2)/SA/PmPD membranes, effectively improving the composite membrane's selectivity and permeability. The resulting Cu-3(PO4)(2)/SA/PmPD membranes exhibited exceptional dye rejection (>98.5 %), high water permeability (>59.0 L m(-2) h(-1) bar(-1)), and long-term operational stability under low-pressure conditions, as well as excellent antibacterial activity (>99 %). This study provides a straightforward approach for fabricating highly permeable multifunctional nanofiltration membranes using the soft spray technique.