Large-Scale MOF Membranes with Ultrahigh Ion Permselectivity for High-Efficient Osmotic Energy Harvesting

Harvesting osmotic energy from seawater–river water interfaces remains challenging due to the intrinsic selectivity–permeability trade-off in conventional ion-exchange membranes. Here, we fabricate large-scale Universitetet i Oslo-66 (UiO-66)/aramid nanofiber (ANF) nanocomposite membranes via an in situ polymerization method as high-performance osmotic energy generators. The UiO-66 layer, with its negatively charged surfaces and subnanometer channels, achieves near-ideal cation selectivity (0.99 and 0.98 under 5-fold and 50-fold concentration gradients), while the ANF scaffold's three-dimensional (3D) fibrous nanochannels enable ultrafast cation diffusion (ionic permeabilities: 3.40 × 104 and 1.97 × 105 S m–2). This synergy effect yields record power densities of 16.46 W m–2 (50-fold) and 100.12 W m–2 (500-fold), surpassing state-of-the-art metal–organic framework (MOF) membranes (Materials of Institute Lavoisiers (MIL), Zeolitic Imidazolate Frameworks (ZIF), etc.) through precise angstrom-scale charge screening. What's more, the high mechanical properties (tensile strength: 314.26 MPa; Young's modulus: 9.96 GPa) endow the composite membranes with the scalable possibility of large-scale salinity gradient power generation. Under an enlarged testing area of 7 mm2, the maximum power density achieved a breakthrough of 1.93 W m–2. Combined with pH-responsive adaptability (140.86 W m–2 at a pH of 11) and 94.6% 30 day stability in harsh salinity gradients (0.01/5 M sodium chloride (NaCl)), this work establishes a paradigm for designing mechanically durable, large-scale nanofluidic systems to harvest blue energy efficiently across estuarine and industrial brine environments.