Enhanced gas separation performance of mixed matrix membranes from graphitic carbon nitride nanosheets and polymers of intrinsic microporosity

In this study, novel kinds of mixed matrix membranes (MMMs) were prepared by incorporating g-C3N4 nanosheets into the matrix of polymers of intrinsic microporosity (PIM-1). The PIM-1/g-C3N4 MMMs were characterized using field emission scanning electron microscope (FESEM), thermal gravimetric analysis (TGA), differential scanning calorimetry (DSC), X-ray diffraction meter (XRD) and an electronic stretching machine. Pure gas permeation tests of the MMMs were conducted for the following gas species: CO2, CH4, N-2 and H-2. Gas permeation properties of the MMMs were rationally tuned with the incorporation of g-C3N4 nanosheets. Firstly, the 2D structural g-C3N4 with high surface area ratio can efficiently affect the packing of PIM-1 polymer chains and create additional transport pathways at the interface between PIM-1 matrix and g-C3N4 filler, which result in an increment of permeability coefficients, especially at low g-C3N4 loadings. Secondly, the periodic ultramicropores of g-C3N4 with size sieving effect can preferentially facilitate the transport of smaller molecules (H-2) and the selectivities for H-2/CH4 and H-2/N-2 were increased without compromise in gas permeability, compared with pure PIM-1 membrane. Meanwhile, the PIM-1/g-C3N4 MMMs also demonstrated better long-term performance with the incorporation of g-C3N4. The ordered 2D-structure, superior interfacial compatibility and easy mass production endow g-C3N4 with promising potential in fabricating gas separation MMMs. (C) 2016 Elsevier B.V. All rights reserved.