Size–Thickness Compatibility: Unlocking the Potential of Nanosheet-Incorporated Membranes

Size-dependent two-dimensional (2D) materials exhibiting permselectivity and structural stability have emerged as promising additives to enhance membrane performance. However, the influence of nanosheet size and its interaction with membrane thickness remain largely unexplored, resulting in a critical gap in the understanding of their contribution to membrane performance. In this study, poly(trimethylsilylpropyne) (PTMSP) membranes incorporating molybdenum sulfide (MoS₂) nanosheets of varying sizes (300, 600, and 1000 nm) were fabricated on polysulfone (PSf) substrates and tested for organic solvent nanofiltration (OSN). The smaller nanosheets (300 nm) demonstrated superior specific surface area and dispersibility, leading to hybrid membranes with enhanced free volume, electronegativity, and mechanical strength. The optimal membrane (MoS₂–PTMSP_300–300) with 2.91 wt % MoS₂ loading achieved a methanol permeance of 8.17 L·m^–2·h^–1·bar^–1 and a rejection of 98.65% for rose bengal (RB). In contrast, larger nanosheets (1000 nm) formed parallel alignments, which negatively impacted membrane permeance. Furthermore, the uniform distribution and strong compatibility of smaller nanosheets with the polymer matrix contributed to the long-term stability of the membranes. These findings highlight the pivotal role of nanosheet size in determining membrane performance, and provide valuable insights for the design of nanocomposite membranes with tunable thickness using size-dependent 2D materials.