Polyamide@GO microporous membrane with enhanced permeability for the molecular sieving of nitrogen over VOC

Mixed matrix membranes (MMMs) are typically fabricated by mechanically mixing presynthesized polymers and fillers together in a solvent to form a membrane solution, which often causes poor filler dispersion in the polymer matrix. In this work, an in situ polymerization method was proposed by which 2,6,14-triaminotriptycene (Trip), octanedioyl chloride, and graphene oxide (GO) reacted in the polymerization to form a polyamide@GO mixed matrix polymer. Different characterization methods, such as Raman analysis, XRD (X-ray diffraction), and TGA (thermogravimetric analysis), were used to verify the chemical linking between GO and polyamide. The performance of the polyamide@GO membrane in the separation of cyclohexane/nitrogen mixtures was evaluated and compared with that of pure polyamide membranes and mechanically mixed polyamide + GO membranes. The polyamide@GO membrane with a GO content of 0.3 wt% exhibited the highest separation performance. The permeability increased from 427 Barrer to 1098 Barrer under the same rejection (99.4%) conditions compared with that of the pure polyamide membrane. Because incorporation of GO disrupted the efficient stacking of polyamide chains, more amorphous domains were formed, providing more transport channels. This work provides an alternative way to overcome the trade-off phenomenon in the synthesis of new MMMs.