Figure 2. Surface morphology of PDMS (a, b) and 15% Ni-ZIF-8 MMM (c, d), cross section image of 15% Ni-ZIF-8 MMM (e, f).
In addition to surface morphologies, the dispersion of Ni-ZIF-8 nanoparticles within the polymer matrix was further verified using the EDX analysis shown in Figure S8. The continuous grey and green colors representing the Si and O, respectively, reflecting Si–O backbone of the polymer matrix. The Si and O colors have filled the mapping, which confirmed that all Ni-ZIF-8 nanoparticles are wrapped with the PDMS layer. The blue, red, and yellow colors are representing the Zn, N, and Ni, respectively. The good distribution of these three colors confirmed the excellent dispersion of Ni-ZIF-8 nanoparticles within the polymer matrix, which might be beneficial to create the relatively continuous pathways for molecular diffusion. In order to improve the separation performance and defect-free membrane synthesis, homogeneous dispersion of the filler, and excellent compatibility between organic and inorganic phases must be created12.
The tests of TGA, EDX, SEM, and EDX revealed that the Ni-ZIF-8 has excellent interaction with PDMS chains, and could activate the Van der Waals forces and hydrogen bonding between Ni-ZIF-8 and polymer phases. Moreover, the addition of Ni-ZIF-8 in the PDMS did not alter the crystallinity and chemical structure of PDMS, as shown by XRD and FTIR analysis.