Preparation of mixed matrix membranes based on polyimide and aminated graphene oxide for CO2 separation

The aminated graphene oxide (GO) was prepared by the functionalization of pristine GO with ethylenediamine and then dispersed into the poly(amic acid) (the precursor of polyimide [PI]) solution followed by the chemical imidization to successfully fabricate the PI/amine-functionalized GO mixed matrix membranes (MMMs) using in-situ polymerization method. Chemical structure and morphology of the GO before and after amine modification were characterized by scanning electron microscopy, Raman spectrum, Fourier transform infrared, and X-ray photoelectron spectroscopy. Scanning electron microscopy indicated that fine dispersion of GO throughout PI matrix was achieved, which indicates that the in-situ polymerization approach can enhance the interfacial interaction between the GO and the PI matrix, and then improve the dispersion of carbon material in the polymer matrix. Compared with the conventional solution mixture method, the MMMs prepared with in-situ polymerization method showed excellent CO2 permeability and CO2/N-2 selectivity. The MMMs doped with 3wt.% aminated GO exhibited maximum gas separation performance with a CO2 permeability of 12.34 Barrer and a CO2/N-2 selectivity of 38.56. These results suggest that the amino groups on GO have strong interaction with the CO2 molecules, which can significantly increase the solubility of polar gas. Our results provide an easy and efficient way to prepare MMMs with good mechanical behavior and excellent gas separation performance.