Electrosprayed polyamide nanofiltration membrane with uniform and tunable pores for sub-nm precision molecule separation

Interfacial polymerized polyamide composite nanofiltration membrane has been widely used in wastewater treatment. Despite its high selectivity towards water and solutes, differentiation of solutes with similar size is still a great challenge. Herein, we propose that polyamide nanofiltration membrane with uniform and tunable pores and sub-nm precision selectivity can be achieved through electrospraying strategy via controlling relative humidity (ratio of practical vapor pressure P 1 and its saturated vapor pressure P s ). The enhanced relative humidity facilitated the dispersion of piperazine (PIP) monomers on substrate and the reaction with trimesoyl chloride (TMC). The membrane (M78) fabricated at high humidity (70%-80%) exhibited more uniform pore size and narrower size region (0.26 nm-0.49 nm) at a designed rejection difference (e.g., 50%) compared with the membrane (0.26 nm-1.0 nm) obtained at low humidity (30%-40%). Membrane selectivity (e.g., Na 2 SO 4 and NaCl) was an order of magnitude high when humidity increased from 30%-40% to 70%-80%. The current study offered a facile and effective strategy for fabricating polyamide nanofiltration membrane with uniform pores and sub-nm selectivity.