Fluorine-Containing Porphyrin-Modified Graphene Oxide Laminar Membranes for Organic Solvent Nanofiltration

Organic solvent nanofiltration (OSN) offers a promising low-energy alternative for separating molecules in the 200–1000 g/mol range. However, conventional polymeric membranes used in water treatment lack sufficient organic solvent resistance. Graphene oxide (GO), a two-dimensional nanosheet material, is a promising candidate owing to its inherent thermal and chemical stability, as well as its characteristic laminar structure in thin films. GO membranes can provide high selectivity through molecular sieving because of the well-defined interlayer spacing between GO nanosheets. Nonetheless, GO membranes suffer from high permeation resistance, as a result of the long, tortuous pathways formed between the high-aspect-ratio GO sheets, significantly impeding solvent penetration. 5,10,15,20-Tetrakis(pentafluorophenyl)porphyrin (TPPF), a hydrophobic and fluorine-rich molecule, is used as an intercalation agent in the present study to alter the chemical environment of the reduced GO (rGO) nanochannels and enhance solvent transport by controlling membrane–solvent interactions. Increasing the TPPF/rGO mass ratio from 0 to 0.4 enhances methanol permeance from 0.49 to 0.60 L m–2 h–1 bar–1. Simultaneously, the rejection of vitamin B12, a model solute, also increases monotonically. This concurrent improvement is attributed to the reduced surface free energy within the permeation channels. TPPF modification increases the channels’ affinity for methanol, facilitating passage through the membrane. Overall, by tuning membrane–solvent interactions, the targeted chemical and physical modification of nanoconfined spaces is an effective approach for designing high-performance and sustainable OSN membranes.