Tuning Thermal Expansion in Metal-Organic Frameworks Using a Mixed Linker Solid Solution Approach.

Area of Science:

• Materials Science
• Chemistry
• Solid-State Physics

Background:

• Metal-organic frameworks (MOFs) are known to exhibit negative thermal expansion (NTE).
• Continuous tuning of thermal expansion from negative to positive in a single MOF phase has not been previously reported.
• Traditional NTE materials lack this tunable characteristic.

Purpose of the Study:

• To investigate the continuous tuning of thermal expansion in a MOF system.
• To explore the formation of single-phase solid solutions for controlling thermal expansion.
• To establish a general strategy for tailoring thermal expansion in MOFs.

Main Methods:

• Synthesis of a series of mixed linker solid solutions in the Zn-DMOF-TM system.
• Characterization of the thermal expansion properties of the synthesized MOFs.
• Analysis of the structural changes influencing thermal expansion behavior.

Main Results:

• A smooth transition from negative to positive thermal expansion was observed in the a-b plane of the tetragonal material.
• The temperature of zero thermal expansion shifted from ~186 K to ~325 K with increasing TM-bdc content.
• Successful formation of single-phase solid solutions enabled continuous thermal expansion tuning.

Conclusions:

• Mixed linker solid solutions represent a viable and general strategy for controlling thermal expansion in MOFs.
• This work demonstrates unprecedented tunability of thermal expansion in a single MOF system.
• The findings pave the way for designing MOFs with specific thermal expansion characteristics.