Solar-driven water-energy-salt nexus enabled by a Ti3C2-F/CuBi2O4-coated membrane.

The growing global demand for freshwater and sustainable energy requires integrated technologies capable of addressing water-energy challenges in a single platform. Here, a multifunctional photothermal architecture is developed by integrating copper bismuth oxide (CuBi2O4; CBO) with a two-dimensional (2D) Ti3C2-F MXene (MX) to form a CBO@MX hybrid, enabling simultaneous solar desalination, electrokinetic energy generation, and salt harvesting. CBO@MX loaded onto a cellulose membrane, is designed to promote directional capillary flow, ensuring sustained saline water supply to the photothermal interface. Synergistic coupling between the semiconducting CBO and MX enables broadband light absorption and efficient conversion into heat, while interlocking nanochannels facilitate ion transport and electrokinetic potential generation through the formation of an electric double layer. Under AM 1.5G solar irradiation, the CBO@MX delivered a high evaporation rate of ∼1.68 kg m-2 h-1 and simultaneously produced a stable open-circuit voltage of ∼0.5 V without any external power input. Moreover, asymmetrical wettability induced self-driven saline water transport and controlled salt crystallization at the membrane periphery, effectively mitigating pore blockage, while enabling simultaneous salt harvesting. The CBO@MX hybrid membrane exhibited stable performance for twenty five consecutive desalination cycles. This study presents a scalable, low-cost, and sustainable strategy for integrating solar-driven desalination with energy harvesting, offering a promising route toward decentralized and off-grid water-energy nexus technologies.