A hydrophobic ionic liquid and ZIF-8 co-modified graphene oxide membrane for efficient osmotic energy conversion

Abstract

Two-dimensional (2D) nanofluidic membranes hold great promise for osmotic energy conversion, yet achieving an optimal balance between ion permeability and selectivity remains a critical challenge. Herein, a spatially confined strategy was employed to in situ grow ZIF-8 nanoparticles and incorporate hydrophobic ionic liquid (HIL) [Bmim][NTf₂] within a laminated graphene oxide (GO) membrane to form a GO/ZIF-8/[Bmim][NTf₂] composite membrane with heterostructured nanochannels. The GO laminates serve as a robust scaffold for the whole system. The in situ growth of ZIF-8 enhances ion permeability and refines selectivity. The incorporation of HIL not only improves the membrane stability in aqueous electrolyte but also forms a continuous medium to optimize the ionic transport environment within the channels. Benefiting from this synergy, the resulting composite membrane achieves an excellent cation selectivity of 0.945 and a power density of 10.4 W m⁻² under a 50-fold NaCl concentration gradient. This strategy is universal for the fabrication of different GO/MOF/HIL composite membranes (such as GO/HKUST-1/[Bmim][NTf₂] and GO/ZIF-8/[Bmim][PF₆]) and provides new insights into the design of high-performance 2D/MOF/HIL composite membranes for osmotic energy conversion.