Two-dimensional superstructures filled into polysulfone membranes for highly improved ultrafiltration: The case of cuprous iodide nanosheets

Mixed-matrix membranes blended with nanosized inorganic fillers have been widely used in ultrafiltration (UF) for large molecule separation. In this work, we provide a feasible route to construct mixed-matrix polysulfone (PSf) UF membranes via the nonsolvent-induced phase inversion process, utilizing sheet-like copper iodide superstructures (s-CuI) as fillers. The size of s-CuI in lateral dimension reaches micrometer scale, but the nanosheets can be well embedded in the polymer matrix with their 2D basal planes parallel to the membrane surface . On account of the stacking straight-through channel structure of s-CuI and its large dimension spanning across multiple membrane pores within the layer, the PSf membrane blended with 0.8 wt% content of s-CuI displays optimal UF performance with a pure water permeation (PWP) of 1473 L/(m 2 h bar) and a bovine serum albumin (BSA) rejection of 92%. In contrast, the pure PSf membrane only presents a PWP of 556 L/(m 2 h bar) and a BSA rejection of 58.2%. Besides, the enhancement of mechanical stability for the PSf/s-CuI 0.8% membrane is significant and the leakage of the s-CuI filler is negligible. Though the antifouling performance of the PSf/s-CuI 0.8% membrane against the protein BSA is limited, its flux is always 2–3 times higher than that of the pure PSf membrane in each step during a sequential test of fouling behavior . This study indicates that it is highly promising to employ designable superstructures as functional fillers to construct novel mixed-matrix membranes with good interfacial compatibility and superior performance.