Self-Standing combined covalent-organic-framework membranes for subzero conductivity assisted by ionic liquids

Area of Science:

• Materials Science
• Electrochemistry
• Polymer Chemistry

Background:

• Proton-conducting materials face challenges in cold environments, limiting applications.
• Covalent organic frameworks (COFs) show promise but require development for subzero operation.

Purpose of the Study:

• To develop flexible, self-standing proton-conductive COF membranes (ssc-COFMs) for operation at subzero temperatures.
• To enhance proton conductivity in COFs by incorporating proton-conducting ionic liquids (PCILs).

Main Methods:

• Fabrication of combined COF membranes (ssc-COFMs) using TpBD-Me2 and Tp-TGCl.
• In-situ encapsulation of proton-conducting ionic liquids (PCILs) into COF backbones.
• Characterization using XRD, FTIR, nitrogen adsorption, and elemental analysis.

Main Results:

• ssc-COFMs exhibit high proton conductivities from 243 K to 353 K.
• Proton conductivity reaches 9.93 × 10⁻⁴ S cm⁻¹ at 243 K (98% RH) with -SO₄H functionalized PCILs.
• Conductivity of 6.84 × 10⁻² S cm⁻¹ achieved at 353 K (98% RH).

Conclusions:

• The developed ssc-COFMs demonstrate significant proton conductivity at subzero temperatures.
• Multifaceted synergistic effects from multiple proton units enhance performance.
• These materials offer a breakthrough for proton conduction in cold regions.