Polyphenol-coordinated liquid metal metallogels integrated with heterogeneous Janus membranes for efficient solar water-electricity cogeneration

Solar evaporation-driven water-electricity cogeneration offers a transformative solution to global water and energy shortages. However, conventional evaporators suffer from poor energy-mass matching, low salt tolerance, and limited system stability. Herein, we report an engineered heterogeneous Janus membrane platform integrating a tannic acid (TA)-mediated eutectic gallium-indium (EGaIn) hybrid photothermal metallogel with a hierarchically structured poly(vinyl alcohol) (PVA)-based Janus membrane. The metallogel features multiple charge-transfer complexes from Ti(IV)/Fe(III) coordination at polyphenol/EGaIn interfaces, enabling broadband solar absorption and efficient localized heat channeling. The underlying Janus substrate, composed of a spherical-beads-on-string (SBS) poly(vinyl alcohol) acetoacetate (PVAA) layer reinforced by 1,4-dihydropyridine (DHP) rings, creates an asymmetric wetting interface that lowers the equivalent water evaporation enthalpy to 1271 J g −1 through intermediate water regulation. The integrated generator achieves a high evaporation rate of 2.58 kg m −2 h −1 and a thermoelectric power density of 285.9 μW cm −2 under 1 Sun illumination. Moreover, the system exhibits excellent salt rejection (>99.9% for major ions), stable operation over 72 h in 3.5 wt% brine, and successful outdoor desalination with a daily water production of ∼13.79 L m −2 . This work provides a scalable and practical heterogeneous interface engineering strategy for developing multi-functional liquid metal/polymer composites toward sustainable water and energy supply.