Hydrogels with rich network chemical components and customizable pore structures have become ideal membrane materials for multiple fields, such as ion sieving, gas separation, and osmotic energy harvesting. However, existing hydrogel membranes suffer from high transport resistance and poor selectivity, mainly because traditional thermally initiated and photo-initiated bulk gelation methods cannot reduce their micrometer-scale thickness and pore size. In this study, we discovered a multifunctional confined gelation platform that uses two-dimensional photothermal nanosheets as triggers,Construct ultra-thin layered hydrogel membranes (LHM) to replace traditional small-molecule thermal and photoinitiators. The LHM assembles photothermal nanosheets in the hydrogel precursors into a layered framework with tunable thickness and sub-nanometer spacing on the surface of a porous substrate, using its size-selective capability to reject assembling nanosheets. Subsequently, confined gelation triggered by photothermal effects occurs only within this layered framework. This approach enables the production of large-scale, uniform LHMs with ultra-stable sub-nanometer channels and an extremely thin thickness of up to 50 nanometers, approximately three orders of magnitude lower than conventional products. By customizing the hydrogel network chemistry, our LHMs can be applied in gas separation, achieving outstanding CO2/N2 selectivity of up to 175, while also harvesting osmotic energy at an impressive maximum power density of 6.87 W/m2 even under long-term operation.

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DOI: 10.1021/acsnano.5c18130