2D Sulfur-Enriched Polymer Nanofilm as a Macroscopic RAFT Agent toward Programmable Ion-Sieving Membranes

Sulfur-containing polymers are promising materials characterized by notable thermal, mechanical, optical, and recyclable properties, but synthesizing them as two-dimensional (2D) nanomaterials remains a significant challenge. Here, we introduce a mild interfacial polymerization (IP) strategy that enables the facile fabrication of large-area, continuous 2D polytrithiocarbonate (PTTC) nanofilms. The resulting nanofilms could be readily transferred to various substrates and used as active layers for separation membranes. Moreover, the PTTC nanofilms serve as macroscopic reversible addition-fragmentation chain-transfer (RAFT) agents, permitting their precise post-synthetic functionalization for reduced pore sizes and engineered surface charge. This programmable modification yields tailored nanofiltration membranes that achieve high ion-pair selectivity (Cl−/SO42−, 87.1; Na+/Mg2+, 22.0), enhanced water flux, and robust stability in harsh acidic environments. This work establishes a versatile platform for creating adaptive 2D polymer films, with promising applications in advanced separations, smart coatings, and sensing technologies.