Covalent Natural Framework Membrane for Osmotic Power

A paper lately revealed within the journal ACS Utilized Power Supplies demonstrated the feasibility of utilizing a covalent natural framework (COF)-based nanofluidic hybrid membranes (NHMs) to realize enhanced interfacial ion transport for the technology of osmotic power.  


​​​​​​​Examine: Improved Interfacial Ion Transport via Nanofluidic Hybrid Membranes Based mostly on Covalent Natural Frameworks for Osmotic Power Technology. Picture Credit score: sakkmesterke/

Significance of Osmotic Power

Osmotic power exists within the type of a salinity gradient between seawater and freshwater and represents a crucial blue power supply. This type of power is used extensively to fulfill the wants of sustainable growth owing to its straightforward accessibility and wealthy reserves.

Limitations of the Present NHMs for Osmotic Power Technology

Reverse electrodialysis is usually used to seize osmotic power via permeable membranes. Particularly, versatile NHMs have gained appreciable consideration as a consequence of their delicate structural properties.

These membranes are fabricated by integrating two purposeful membranes and have asymmetrical geometric configuration, chemical composition, and floor cost, which contribute to the membrane’s distinctive ionic transport conduct.

Thus, a number of osmotic power conversion programs have been developed based mostly on NHMs, reminiscent of ionomer-based nanofluidic diode membranes and polyethylene terephthalate (PET)/block copolymer heterogeneous membranes.

Nevertheless, the low energy densities/extraordinarily restricted output energy of the NHMs as a result of low effectivity/inefficient interfacial ion transport made them unviable for business purposes.

The inefficient interfacial ion transport is brought on by the pore alignment mismatch between the interface of two purposeful layers and a restricted variety of pores. These limitations necessitated the event of enhanced osmotic power conversion units based mostly on NHMs with ample ion transport and plentiful selective pores.

Novel Methodology to Develop an Efficient NHM 

COFs, a brand new sort of porous crystalline polymers, are shaped by the covalent linking of natural constructing blocks via covalent bonds. These crystalline polymers possess nanospaces that may be functionalized, well-ordered channels, and ultrahigh porosity. Total, this makes them an appropriate platform for environment friendly interfacial ion transport.

Moreover, these modified nanospaces of COFs will be utilized to manage ion selectivity intelligently. A number of research have demonstrated novel ion transport conduct within the COF membrane.

For example, polyethylene glycol-modified COFs present a quick ion transport pathway, which is appropriate for designing high-performance ion conductors. Thus, the COF membrane generally is a promising candidate for reaching environment friendly interfacial ion transport in NHM.

Synthesis and Analysis of COF-based NHM 

On this research, researchers synthesized an NHM containing ultrahigh pore density COF- Lan Zhou College-1 (COF-LZU1) layer and cellulose nanofibers/carbon nanotubes (CNF-CNT) membrane to realize environment friendly conversion of the ionic gradient to electrical energy. The synthesized membrane was designated as [email protected]

1,4-dioxane (Diox), 1,3,5-benzene-tri carboxaldehyde (TFB), tetrahydrofuran, 1,4-diaminobenzene (PDA), acetic acid (HAc), acetone, CNT suspension, and CNF gel have been used because the beginning supplies for the research. A Millipore direct-Q system was used to provide ultrapure water for experiments.

Synthesis of COF-LZU1 Nanoseeds

TFB and Diox have been combined and stirred for quarter-hour after which PDA was added to the as-prepared resolution. The resultant combination was once more stirred for 20 minutes. Subsequently, a yellow suspension was noticed after HAc was added to the as-obtained resolution. The suspension was left undisturbed for twenty-four hours at room temperature.

The obtained COF-LZU1 nanoseeds have been centrifuged, cleaned with Diox, tetrahydrofuran, and acetone, and activated by methanol in sequence. Ultimately, the nanoseeds have been vacuum dried at 80 levels Celsius for twenty-four hours.

Synthesis of CNF-CNT Membrane

The CNT suspension and CNF gel have been initially combined with water and stirred vigorously. CNF-mixed CNT membrane was then obtained by vacuum filtration of part of the combined suspension.

Fabrication of [email protected] NHM

Initially, the synthesized COF-LZU1 nanoseeds have been spin-coated on the CNF-CNT movie, and the coated facet of the movie was then submerged in a combination of PDA, TFB, and Diox. The temperature of the resultant development resolution was maintained at 50 levels Celsius for six hours to acquire [email protected] NHM.

Analysis of the Synthesized Samples

The osmotic power conversion and ion transport conduct of the synthesized membranes have been investigated utilizing the Keithley 6487 picoammeter. A pair of silver/silver chloride electrodes have been used to use the transmembrane potential. Throughout the ion transport measurement, the working electrode was mounted on the CNF-CNT facet.

Researchers additionally systematically studied the affect of a number of exterior elements, reminiscent of electrolyte species, temperature, and pH, on salinity gradient power conversion efficiency.

Significance of the Examine

[email protected] with typical NHM traits was synthesized efficiently by the hybridization of the CNF-CNT membrane and purposeful COF-LZU1 layer. The hybridization of two layers considerably elevated the effectivity of interfacial ion transport and promoted osmotic power conversion.

The CNF-CNT membrane with quite a few carboxylic acid teams interacted with the COF-LZU1 amino teams to type an efficient hybrid membrane. The well-organized and plentiful pores of the COF-LZU1 layer ensured ample ion transport, whereas the interlaced CNF-CNT membrane offered a three-dimensional (3D) charged house to modulate the ion transport.

Furthermore, the fragile design of the synthesized membrane tremendously facilitated the interfacial ion transport throughout the membrane by constraining the ion polarization impact and contributing to ion diffusion.

A considerably excessive energy density of 4.26 watts per sq. meter was attained when the synthesized membrane was utilized in an power conversion machine to seize the osmotic power saved between river water and pure seawater.

Taken collectively, the findings of this research demonstrated the effectiveness of [email protected] NHM in reaching high-efficiency interfacial ion transport for osmotic energy technology and bolstered the appliance of COF membranes on this subject.


Wang, S., Wang, Q., Li, R. et al. (2022) Improved Interfacial Ion Transport via Nanofluidic Hybrid Membranes Based mostly on Covalent Natural Frameworks for Osmotic Power Technology. ACS Utilized Power Supplies.

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