Nanomaterials - 03

Abstract

Osmotic energy harvesting is a highly promising decarbonization technology, in which advanced anion-exchange membranes play a pivotal role. It is of great interest to develop advanced anion-exchange membranes based on two-dimensional materials [1]. Our group demonstrated that single layered double hydroxide (LDH) nanosheets exhibited exceptionally high and anisotropic hydroxide ion conductivity [2]. In this work, positively charged MgAl- LDH nanosheets and imine-bridged covalent organic frameworks (COFs) were combined to construct organic-inorganic composite membranes. First, single-layer MgAl-LDH nanosheets with micrometer-scale lateral dimensions (~0.8 nm in thickness), and imine-bridged COF platelets (~10 nm in thickness) were synthesized. A self-supporting composite membrane was then prepared by vacuum filtration of a mixed LDH/COF suspension. The incorporation of COF nanoparticles disrupted the lamellar stacking arrangement of LDH nanosheets, thereby diversifying ion transport pathways. Impedance spectroscopy measurements confirmed that the LDH/COF composite membranes exhibited enhanced anion conductivity compared with that of pure LDH. By combining LDH nanosheets with COF nanoparticles, the composite also exhibited improved anion selectivity, underscoring its potential for osmotic energy harvesting.