Bilayer asymmetric-based metal-organic frameworks membrane for blue energy conversion

[Graphical abstract presents]

The conversion of Gibbs free energy at the interface of solutions with salinity gradients into electrical energy is essentially a means of mitigating environmental pollution and bolstering the availability of new energy sources to enhance the renewable energy portfolio. However, a three-dimensional (3D) sub-nanofluidic membrane with high ion conductivity and selectivity for a reverse electrodialysis (RED) based osmotic energy conversion in both aqueous and organic solutions remains largely unexplored. Herein, we engineered a bilayer metal organic frameworks (MOFs) membrane with polystyrene sulfonated angstrom-size channels in UiO-66-NH₂ base layer and isoreticular MIL-88B membrane as the top layer to enhance permselectivity and high-performance salinity gradient energy generation. The angstrom-size windows in the heterogeneous membrane with a negatively charged channel surface endow the UiO-66-NH₂(PSS)/MIL-88B membrane with a preferred direction of ion conduction. Collectively, these features of the bilayer angstrofluidic channel membrane promote diffusion-driven osmotic energy conversion of 32.46 Wm⁻² and permeability of 526.60 Am⁻² at the interface of 500-fold aqueous work condition and 3.89 Wm⁻² from 100-fold salinity gradient in LiCl-methanol. This work sheds light on the design and development of novel high-performance sub-nanochannel membranes for osmotic energy generation with high efficiency in both aqueous and waste organic solvents.