Highly selective polyphenylene sulfide nanocomposite membranes based on two-dimensional metal–organic frameworks for molecular separation

Abstract

Two-dimensional MOF nanomaterials with planar spacing and porosity can effectively transport water molecules and have a wide range of applications in dye wastewater treatment. In this work, two types of nanosheets, Cu-TCPP and Zn(Bim)(OAc), were loaded onto polyphenylene sulfide(PPS) ultrafiltration membranes by vacuum-assisted self-assembly, and stable Cu-TCPP/Zn(Bim)(OAc) composite membranes were prepared by taking advantage of the hydrogen bonding and π-π conjugation between the two types of nanosheets. Cu-TCPP/Zn(Bim)(OAc) 2:1 composite membrane showed an optimum selectivity of 97.8% and a permeability of 14.6 L m⁻² h⁻¹ bar⁻¹ for aqueous rhodamine B. The surface morphology, chemical environment and properties of the composite membranes were analyzed using scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), contact angle measurement (DSA) and zeta potential. The rejection rates of the five dyes, saffron T (ST), eriochrome black T (BT), rhodamine B (RB), crystal violet (CV)and Congo red (CR), were 95.8%, 98%, 97.8%, 97.2% and 98.8%, respectively. After immersion in 0.5 mol of different acids, the rejection rate of Congo red dye still reached 96%, composite membrane has good acid resistance. The interaction between the surface groups of the two MOF materials not only resulted in better separation effect, but also gave the composite membrane better contamination resistance and stability. This method of using two-dimensional MOF materials to construct the selective layer of composite membranes has good application prospects.