Hydrophobic poly(vinylidene fluoride) / siloxene nanofiltration membranes

Hydrophobic, chemically resistant nanofiltration (NF) polymeric membranes could provide major improvements to a wide range of processes, from pharmaceutical manufacturing to hazardous waste treatment. Here, we report the fabrication of the first poly (vinylidene fluoride) (PVDF) NF membranes retaining their hydrophobicity and surface chemistry. This was achieved by incorporating in the polymer 2D siloxene, which induce a compaction of the PVDF chains, resulting in low free volume and a highly ordered microstructure. Siloxene nanosheets were obtained from deintercalation of Ca from CaSi2 using HCl, followed by exfoliation and size fractionation, with average lateral dimension of 1–2 μm and thickness of 3–4 nm. The resulting membranes, containing 0.075 wt% of siloxene, have a pure water permeance of 22 ± 2 L m-2 h-1 bar-1 and molecular weight cut-off (MWCO) of 530 Da. The same membrane also showed stable hexane permeance of 11 L m-2 h-1 bar-1 for 24 h with MWCO of around 535 Da. These results supersede the performance of commercial NF membranes, expanding the potential application of nanofiltration to processes requiring stable, chemically resistant and hydrophobic nanofiltration membranes.