Nanodomain Control in Carbon Molecular Sieve Membranes via Nanomaterial Footprinting

Carbon molecular sieve (CMS) membranes, fabricated via pyrolysis, are attracting attention owing to their stability under harsh environments, including high temperatures, organic media, and extreme pH. Herein, the fabrication of composite CMS (CCMS) membranes by incorporating sphere-shaped C60(OH) and ellipsoid-shaped C70(OH) fullerenol nanomaterials into intrinsically microporous 4,4 '-(hexafluoroisopropylidene) diphthalic anhydride 3,3 '-dimethyl-naphthidine polyimide is reported. The encapsulation of the nanomaterials by the polymer matrix, their chemical footprint, and the variation in the local chemistry of the pyrolyzed membranes are successfully revealed via nanodomain analysis using nano-Fourier-transform infrared spectroscopy. The incorporation of fullerenol nanomaterials into CMS membranes can induce the formation of fractional free volume upon pyrolysis, which can translate into molecular sieving enhancement. The effects of the concentration and geometrical shape of the fullerenol nanomaterials are successfully correlated with the membrane separation performance. The CCMS membranes demonstrate excellent stability and pharmaceutical and dye separation performance in organic media. Herein, nanodomain control is pioneered in CCMS membranes via nanomaterial footprinting to induce porosity during pyrolysis and subsequent control molecular sieving performance. Synergetic effects of pyrolysis and fullerenol incorporation on the properties and performance of integrally skinned asymmetric composite carbon molecular sieve (ISA-CCMS) membranes are reported. The design methodology builds on five essential pillars: 1) the geometrical aspects of nanomaterials, 2) nanomaterial dispersibility, 3) heat-induced phase transformation of nanomaterials, 4) encapsulation of nanomaterials by polymer matrices, and 5) nanodomain footprinting and local chemical analysis of the ISA-CCMS membrane.image (c) 2023 WILEY-VCH GmbH

Automated summary

This paper reports the fabrication of composite carbon molecular sieve (CCMS) membranes by incorporating fullerenol nanomaterials into a polyimide matrix. The encapsulation of nanomaterials, their chemical footprint, and the variation in the local chemistry of the pyrolyzed membranes are successfully revealed. The incorporation of fullerenol nanomaterials enhances the molecular sieving effect and improves the separation performance in organic media.