Scalable fabrication of integrated covalent organic framework membrane with selective ion transport for efficient salinity gradient energy harvesting

Abstract

Interfacial polymerization (IP) is a promising approach for preparing covalent organic framework (COF) membranes in energy storage and conversion applications. However, it is a great challenge for traditional IP with water-organic phase to obtain pre-designable and robust COF membranes. Herein, a "one-pot" organic-organic IP/in situ integration approach, constructing three typical β-ketoenamine COF composite membranes with a maximum area of > 600 cm², are reported. The dual organic phases exhibit comprehensive solubility to precursors, facilitating the synthesis of more types of COFs. In this "one-pot" approach, the porous supporting substrate is in situ formed underneath the COF layer via variable-temperature evaporation of two organic solutions without transfer process. It makes some substrate polymers embedded into the COF layer and accomplishes the interlock of two layers at the interface, producing a robust composite membrane. The prepared COF composite membrane exhibits effective sieving capability for Na⁺/Mg²⁺ and achieves a maximum power density of over 1 W m⁻² in the reverse electrodialysis power generation, even using the Na⁺/Mg²⁺ mixed solution. This approach allows for preferably customization of membrane structures, which can expand the applications of COF membranes in separation.