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/(m² h bar) and a bovine serum albumin (BSA) rejection of 92%. In contrast, the pure PSf membrane only presents a PWP of 556 L/(m² 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.