Hydrogen bonding in porous organic framework membranes facilitates stable acid recovery and power generation

A major challenge in treating acidic wastewater containing heavy metal ions lies in the scarcity of membranes that simultaneously exhibit high proton permeability, selectivity, and chemical stability. Here, we report a hydroxyl-functionalized porous organic framework (POF) membrane with an engineered hydrogen bonding network that addresses these limitations. The introduction of hydroxyl groups not only enables the formation of hydrogen bonds, which can shield imine bonds from hydrolysis under acid attack, but also provides an efficient pathway for Grotthuss proton hopping, facilitating rapid proton transport. Concurrently, the functional groups enable strong coordination with heavy metal ions, which reduces the effective pore size and significantly suppresses their diffusion, while leaving proton mobility largely unaffected. As a result, the membrane achieves a high proton permeability of 2.96 mol·m⁻²·h⁻¹ and a proton/Fe³⁺ selectivity of 3780. Furthermore, during acid recovery, the membrane generates remarkable osmotic power with a power density up to 37.62 W·m⁻². This work provides a scalable strategy for designing stable, high-performance proton-conductive membranes and demonstrates their dual functionality in acidic wastewater treatment and renewable energy harvesting.