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

Abstract

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.

Asymmetric Nanoporous Alumina Membranes for Nanofluidic Osmotic Energy Conversion

“…Covalent organic frameworks (COFs), constructed from organic linkers, possess intrinsic structures and customizable organic linkers, which confer COFs with low density, large surface area, tunable pore size and structure, as well as easily modifiable functionality [55] . These properties attract increasing interests in different fields including osmotic energy conversion [26,56–63] . Kuo et al [56] .…”

“…The presence of functional groups within these nanopores offers a promising avenue to achieve both high ion selectivity and permeability for osmotic energy harvesting, owing to the enhanced electrostatic interaction between ions and porous frameworks [64] . Furthermore, these functionalizable nanospaces can be intelligently regulated to control ion selectivity [57] . However, despite significant progress made in controlling MOFs membranes using certain methods, regulating dense MOFs membranes with charged functional groups remains challenging [64] .…”

“…[55] These properties attract increasing interests in different fields including osmotic energy conversion. [26,[56][57][58][59][60][61][62][63] Kuo et al [56] utilized the high porosity of small pores and ordered one-dimensional (1D) channels of COF (Figure 4A) to develop a sub 2 nm-scale ionic diode membrane (denoted as TFP-TPA COF@ANM). The design of asymmetric surface charges and an ordered micro-to macroporous structure endow the COF-based ionic diode membrane with high rectification ability.…”

Membranes for Osmotic Power Generation by Reverse Electrodialysis

“…The COF-LZU1 is prepared from a reaction between 1,3,5-Benzenetricarboxaldehyde and 1,4-diaminobenzene. A 4.26 Wm −2 maximum power density is obtained from a 50-fold salinity gradient of NaCl using the hybrid membrane [ 114 ].…”

Designing Nanofluidic Diode from a Hybrid‐Bilayer Covalent Organic Framework: Molecular Simulation Investigation

“…Recently, hybrid membranes of COF‐LZU1 and carbon nanotube/cellulose nanofiber were found to increase interfacial ion transport efficiency and possess diode behavior, which was attributed to the asymmetrical geometry configuration and charge distribution under a high pH condition. [ 30 ] After the submission of the current study, an ionic diode COF membrane was reported by comprising two oppositely charged COFs (TpPa‐SO 3 Na and TpEB) and demonstrated efficient osmotic energy conversion. [ 31 ]…”