In Situ Growth of Imine-Bridged Anion-Selective COF/AAO Membrane for Ion Current Rectification and Nanofluidic Osmotic Energy Conversion

摘要

Facing the energy crisis, using the salinity gradient between seawater andfreshwater for osmotic energy conversion is a direct way to obtain energy. Sofar, most nanofluidic membranes utilized for osmotic energy generation arecation-selective. Given that both anion- and cation-selective membranes havethe identical importance for energy conversion devices, it is of greatsignificance to develop anion-selective membranes. Herein, an anion-selectivemembrane is synthesized by in situ growth of imine-bridged covalent organicframework (COF) on ordered anodic aluminum oxide (AAO) at roomtemperature. The imine groups and residual amino groups of COF cancombine with protons in neutral solution, enabling the COF positivelycharged and efficiently transport of anions. Particularly, due to the asymmetryin the charge and structure of COF/AAO, the as-prepared membrane exhibitsexcellent ionic current rectification property, which can inhibit ionconcentration polarization effectively and possess high ion selectivity andpermeability. Using the present COF/AAO membrane, salinity gradient energycan be successfully harvested from solutions with high salt content, and theoutput power density reached 17.95W m~(?2) under a 500-fold salinity gradient.The study provides a new avenue for construction and application ofanion-selective membranes in the smart ion transport and efficient energyconversion.