High Flux\nThin Film Nanocomposite Membranes Based\non Metal–Organic Frameworks for Organic Solvent Nanofiltration

Abstract

Thin-film nanocomposite membranes\ncontaining a range of 50–150\nnm metal–organic framework (MOF) nanoparticles [ZIF-8, MIL-53­(Al),\nNH₂-MIL-53­(Al) and MIL-101­(Cr)] in a polyamide (PA) thin\nfilm layer were synthesized via in situ interfacial polymerization\non top of cross-linked polyimide porous supports. MOF nanoparticles\nwere homogeneously dispersed in the organic phase containing trimesoyl\nchloride prior to the interfacial reaction, and their subsequent presence\nin the PA layer formed was inferred by a combination of contact angle\nmeasurements, FT-IR spectroscopy, SEM, EDX, XPS, and TEM. Membrane\nperformance in organic solvent nanofiltration was evaluated on the\nbasis of methanol (MeOH) and tetrahydrofuran (THF) permeances and\nrejection of styrene oligomers (PS). The effect of different post-treatments\nand MOF loadings on the membrane performance was also investigated.\nMeOH and THF permeance increased when MOFs were embedded into the\nPA layer, whereas the rejection remained higher than 90% (molecular\nweight cutoff of less than 232 and 295 g·mol^–1 for MeOH and THF, respectively) in all membranes. Moreover, permeance\nenhancement increased with increasing pore size and porosity of the\nMOF used as filler. The incorporation of nanosized MIL-101­(Cr), with\nthe largest pore size of 3.4 nm, led to an exceptional increase in\npermeance, from 1.5 to 3.9 and from 1.7 to 11.1 L·m^–2·h^–1·bar^–1 for MeOH/PS\nand THF/PS, respectively.