Maximizing Ion Permselectivity in MXene/MOF Nanofluidic Membranes for High-Efficient Blue Energy Generation

Both ion permeability and selectivity of membranes are crucial for nanofluidic behavior. However, it remains a long-standing challenge for 2D materials to balance these two factors for osmotic energy harvesting. Herein, the MXene/metal-organic framework (MOF) hybrid membranes are reported to realize efficient ion-permselective nanofluidic system, leading to high-performance osmotic power generator. In the system, zeolitic imidazolate framework-8 (ZIF-8) is deposited onto the MXene surface and intercalated between the MXene nanosheets by electropolymerization approach. The angstrom-sized windows of ZIF-8 layer act as ion selectivity filters, endowing the membrane with high cation selectivity by size effect. The intercalation of ZIF-8 crystals, reduces the interspacing of MXene, therefore, not only enhancing the ion permeability by shortening the ion transport pathway through the membrane, but also further improving the selectivity by increasing the overlap effect of electric-double layer. The maximum power density reaches up to 48.05 W m(-2) under 500-fold salinity gradient with a high permeability (1263.3 A m(-2)), and a high selectivity of 0.906 at 50-fold is obtained. This study provides a facile method to fabricate nanofluidic 2D membranes with both high ion permeability and selectivity for water nexus energy conversion.

Automated summary

This study reports the development of MXene/MOF hybrid membranes, which can enable efficient ion-permselective nanofluidic systems for high-performance osmotic power generation. By depositing ZIF-8 layer between MXene nanosheets, the membrane achieves high cation selectivity and permeability, resulting in improved efficiency for osmotic power generation.