Multilayered graphene oxide membrane with precisely controlled interlayer spacing for separation of molecules with very close molecular weights

Precise interlayer spacing control and stability improvement had been two main challenges for preparation of high performance multilayered graphene based membrane (MGM). In this study, UV irradiation was adopted to precisely regulate and stabilize the interlayer spacing of a nanofiltration MGM. The UV irradiation on the GO suspension would homogenously and precisely tune the content of the oxygen containing groups on the rGO nanosheets, which should be responsible for uniformly formed interlayer spacing of MGM after assembly. The actual pore size of MGM was estimated through the probability density function model, which was highly uniform and logarithmically decreasing with the increasing UV reduction time. Owing to the uniformly and precisely (in sub-nanometer scale) controlled pore size of MGM, two molecules with a very low molecular weight difference at about 130 Da were completely separated by the MGM prepared from rGO reduced by UV for 8 h. The in-situ AFM nanoindentation as well as the long-term filtration test proved the stability of MGM was dramatically enhanced through the UV reduction and could ensure the practical applications of MGM. This study proposed a facial and scalable protocol to prepare high separation resolution multilayered graphene based NF membrane, which indicated great potential for separation of molecules with very close molecular weights in practical.