Dimensional Evolution from a Giant Molybdenum-Red Cage-like {Mo₂₀₀} to 1D Chains Enabling Ultrahigh Proton Conduction

Area of Science:

• Inorganic Chemistry
• Materials Science
• Nanotechnology

Background:

• Controlled assembly of giant polyoxometalates (POMs) into complex architectures is challenging.
• Understanding structure-property relationships in POMs is crucial for advanced applications.

Purpose of the Study:

• To synthesize and characterize novel giant molybdenum-red POMs with unique architectures.
• To investigate the structure-property relationships, particularly proton conductivity, of these new POMs.

Main Methods:

• Utilized phenylphosphonate ligands to induce novel building blocks ({Mo5L}, {Mo5L}*).
• Employed X-ray crystallography and other analytical techniques to determine the structures of the nanocage ({Mo200}) and 1D chain ({Mo198}).
• Measured proton conductivity under various temperature and humidity conditions.

Main Results:

• Successfully synthesized a 204-nuclearity hollow nanocage ({Mo8}@{Mo200}) with a host-guest architecture and a 1D chain derivative ([{Mo8}@{Mo198}{Mo8}]n).
• The nanocage features a large internal cavity and undergoes symmetry breaking during assembly.
• The 1D chain exhibits continuous proton-conductive pathways.
• Achieved high proton conductivity: 8.28 × 10⁻² S cm⁻¹ for the nanocage and 1.28 × 10⁻¹ S cm⁻¹ for the 1D chain.

Conclusions:

• Demonstrated a new method for constructing complex POM architectures, expanding the library of giant molybdenum-red clusters.
• Established a new paradigm for designing high-performance solid-state proton conductors based on dimensional evolution of POMs.
• The synthesized POMs show potential for applications in energy storage and conversion devices.