Graphene-like MOF nanosheets stabilize graphene oxide membranes enabling selective molecular sieving

Thin laminar membranes assembled by 2D nanomaterials evince the potential to achieve rapid and efficient molecular transport due to precisely amendable in-plane pores and interlayer distances. Despite the extensive use of graphene oxide (GO) membranes for water treatment, water-induced instability and the barrier effect remain challenging issues to be addressed. Here, a water-stable, graphene-like MOF nanosheet (Cu-TCPP) was implemented as a framework bridge to stabilize the GO laminates against swelling and redispersion into water. A stable heterostructure was established by the electrostatic interaction between porphyrin and oxygen-containing groups, and metal coordination of the carboxyl groups of GO nanosheets. The presence of ultrathin Cu-TCPP nanosheets promotes the formation of a nano-wrinkled surface with vertical-slit and in-plane pores that dominate the significantly improved water transport. The resultant composite membranes evince a 7-fold-higher water permeance (165.2 L m-2 h-1 bar- 1) than that of GO membranes with remarkable solute retention (Congo red: 99.1%). Furthermore, this membrane shows an excellent sieving ability either for RB5/MO solutions or for CR/salt mixtures, while achieving a remarkable antibacterial activity against E. coli. The combination of rigid and flexible nanosheets opens an avenue to construct a water-stable multi-channel frame for the next generation of porous 2D materials for water purification.

Automated summary

A stable composite membrane was developed by utilizing Cu-TCPP nanosheets to stabilize GO membranes, resulting in significantly improved water permeance and remarkable solute retention.