Graphene oxide assisted assembly of superhydrophilic MOF-based membrane with 2D/3D hybrid nanochannels for enhanced water purification

Assembling metal-organic framework (MOF) microcrystals into macroscopic membrane structure is of vital importance for the development of high-performance MOF-based membranes. However, most MOFs possess poor solution processibility due to their low colloidal and chemical stability. Herein, we report a facile approach that uses graphene oxide (GO) as two-dimensional (2D) nano-surfactant to assist the dispersion and assembly of superhydrophilic amino acid-based Zr-MOF microcrystals, MIP-202(Zr), into a bulge-structured membrane. The incorporation of superhydrophilic MIP-202(Zr) with GO laminates endowed the resultant membrane with desired two-dimensional/three-dimensional (2D/3D) hybrid nanochannels and stronger hydrophilicity. Benefiting from these features, the obtained GO/MIP-202(Zr) membrane exhibited superior water permeance than pure GO membrane and many other GO/MOF composite membranes. The strengthened permeation performance could also be well-maintained with satisfied rejection performances when utilized for dye molecule rejection. The dye molecule rejection process was closely associated with their size, charge and configuration. Moreover, the GO/MIP-202(Zr) membrane showed improved antifouling performance compared with pure GO membrane, demonstrating its superiority in the practical separation process. Our results provide essential reference values for the assembly of MOF microcrystals into macroscopic membrane structures and their application in water treatment.