Large Negative Linear Compressibility in InH(BDC)₂ from Framework Hinging.

Area of Science:

• Materials Science
• Solid State Chemistry
• Crystallography

Background:

• Negative linear compressibility (NLC) describes materials expanding in one direction under uniform compression, a phenomenon desired in materials science.
• Existing NLC materials often have limited compressibility values (typically < -20 TPa⁻¹) and can involve hazardous components.
• Achieving large NLC is crucial for developing advanced materials with unique mechanical properties.

Purpose of the Study:

• To investigate and characterize a novel material exhibiting exceptionally large negative linear compressibility.
• To explore the structural mechanisms responsible for extreme NLC in the studied material.
• To assess the safety and cost-effectiveness of the new NLC material compared to existing options.

Main Methods:

• High-pressure X-ray diffraction experiments were conducted to analyze the structural response of the material under pressure.
• The compressibility of the material was precisely measured to quantify its NLC value.
• The crystal structure and framework dynamics were analyzed to understand the mechanism of NLC.

Main Results:

• The β-quartz-like InH(BDC)2 material demonstrated an unprecedented extreme NLC of -62.4 TPa⁻¹.
• The observed NLC is attributed to a framework hinging mechanism within the material's structure.
• InH(BDC)2 presents a safer and more economical alternative to NLC materials containing Au⁺/Ag⁺ or CN⁻.

Conclusions:

• Flexible frameworks, particularly those with negative thermal expansion properties, are promising candidates for large NLC.
• β-quartz-like and related frameworks, utilizing rigid linear ligands and flexible angles, are predicted to yield significant NLC.
• The discovery of InH(BDC)2 opens new avenues for designing and synthesizing advanced materials with tunable compressibility.