Bioinspired Angstrom-Scale Heterogeneous MOF-on-MOF Membrane for Osmotic Energy Harvesting

Area of Science:

• Materials Science
• Energy Science
• Electrochemistry

Background:

• Salinity gradient energy generation using reverse electrodialysis (RED) offers a sustainable energy source.
• Efficient RED requires membranes with high ion transport and selectivity, a challenging balance to achieve.
• Metal-organic frameworks (MOFs) show promise for membrane applications due to tunable structures.

Purpose of the Study:

• To fabricate a novel hybridized bilayer MOF-on-MOF membrane for enhanced osmotic power generation.
• To improve both ion transport and selectivity simultaneously in a single membrane architecture.
• To investigate the performance of the developed membrane for salinity gradient energy harvesting.

Main Methods:

• Fabrication of a heterogeneous membrane with ZIF-8 deposited on a PSS-intercalated UiO-66-NH2 film.
• Utilizing angstrom-scale cavities in ZIF-8 for ion selectivity via size exclusion.
• Employing the PSS-intercalated UiO-66-NH2 layer for cation permeability.
• Characterizing the synergistic effects of the bilayer structure on transmembrane conductance.

Main Results:

• The MOF-on-MOF membrane achieved a power density of 40.01 W/m² under a 500-fold concentration gradient.
• A high permeability of 665 A/m² was recorded at 3 KΩ.
• The membrane demonstrated 9.20 W/m² power generation from mixing real sea-river water.
• Simultaneous enhancement of ion transport and selectivity was observed due to overlapped electric double layers.

Conclusions:

• The developed MOF-on-MOF membrane offers a rational design strategy for improved salinity gradient energy harvesting.
• This hybrid membrane technology shows significant potential for the water-energy nexus.
• The findings highlight the effectiveness of combining different MOFs for advanced membrane functionalities.