Superprotonic conduction through one-dimensional ordered alkali metal ion chains in a lanthanide-organic framework

Area of Science:

• Materials Science
• Inorganic Chemistry
• Solid-State Chemistry

Background:

• Proton conductivity in materials is crucial for energy applications like fuel cells.
• Metal-organic frameworks (MOFs) are promising candidates for proton conduction due to their tunable structures.
• Developing MOFs with high proton conductivity, especially under varying conditions, remains a significant challenge.

Purpose of the Study:

• To synthesize and characterize a novel anionic lanthanide-organic framework.
• To investigate the proton conductivity and conduction mechanism of the synthesized material.
• To evaluate the potential of lanthanide-based MOFs for advanced proton-conducting applications.

Main Methods:

• Synthesis of the anionic lanthanide-organic framework Na2[Eu(SDB)2(COO)]·0.375DMF·0.4H2O (1).
• Measurement of proton conductivity at 363 K and 90% relative humidity (RH).
• Determination of activation energy for proton conduction.
• Analysis of the conduction mechanism, potentially involving the Grotthuss mechanism.

Main Results:

• The framework Na2[Eu(SDB)2(COO)]·0.375DMF·0.4H2O (1) achieved an ultrahigh proton conductivity of 2.91 × 10-2 S cm-1.
• An ultralow activation energy of 0.10 eV was recorded, indicating efficient proton transport.
• The observed conductivity and low activation energy approach record values for proton-conducting MOF materials.
• Proton conduction appears to follow a Grotthuss-like mechanism, facilitated by aligned Na+ ions and coordinated water molecules.

Conclusions:

• The synthesized anionic lanthanide-organic framework demonstrates exceptional proton conductivity.
• The material offers an effective proton transportation pathway, suggesting potential for high-performance proton conductors.
• This work highlights the promise of lanthanide-based MOFs in advancing proton conduction technologies.