Improved Interfacial Ion Transport through Nanofluidic Hybrid Membranes Based on Covalent Organic Frameworks for Osmotic Energy Generation

Nanofluidic hybrid membranes integrated with asymmetrical surface charge, chemical composition, and geometric configuration exhibit unprecedented advantages in capturing the osmotic energy between river water and seawater. However, the output power is very restricted by the inefficient interfacial ion transport of the permselective membranes caused by the low-density pores and mismatch of the pore alignment. In this work, we developed a nanofluidic hybrid membrane constructed by ultrahigh pore-density covalent organic frameworks COF-LZU1 (Lan Zhou University-1) with the carbon nanotube/cellulose nanofiber (CNT-CNF) membrane. The COF-LZU1 layer possesses well-ordered and high-density pores, ensuring abundant selective ion transport. The CNT-CNF membrane functions as a robust support and also offers 3D charged space for the enhanced ion transport. The hybridization of the two layers dramatically increases the interfacial ion transport efficiency. Employing the COF-LZU1@CNT-CNF nanofluidic hybrid membrane to capture the osmotic energy stored between natural sea water and river water, a considerably high power density of 4.26 W m-2 is attained. This delicate design strategy offers ideas for the application of COF membranes in osmotic energy conversion.