Direct Sintering Behavior of Metal Organic Frameworks/Coordination Polymers.

Area of Science:

• Materials Science
• Chemical Engineering
• Crystallography

Background:

• Metal-organic frameworks/coordination polymers (CPs) are versatile materials with potential applications in various fields.
• Understanding the processing of CPs, such as sintering, is crucial for their practical implementation.
• Distinguishing sintering behavior between melting and non-melting CPs is key for material processing optimization.

Purpose of the Study:

• To investigate the sintering behavior and mechanisms of melting ([Zn(HPO4)(H2PO4)2]·2H2Im, ZPI) and non-melting (ZIF-8) CPs.
• To characterize the physical and microstructural changes during CP sintering.
• To correlate sintering parameters with macroscopic properties like shrinkage and density.

Main Methods:

• Compaction and subsequent sintering of ZPI and ZIF-8 CPs.
• Physical characterization including measurement of shrinkage and apparent density.
• Microstructural analysis to understand sintering mechanisms at different temperatures.

Main Results:

• Sintering behavior is dependent on temperature, heating rate, and CP properties, particularly meltability.
• Melting CP (ZPI) showed significant shrinkage (10-20%) driven by localized melting, while non-melting ZIF-8 showed <1% shrinkage.
• Increased sintering temperature led to decreased apparent density in ZPI, indicating complex structural changes beyond simple densification.

Conclusions:

• Localized melting is a dominant sintering mechanism for melting CPs at higher temperatures.
• Significant shrinkage in melting CPs does not necessarily translate to increased material density.
• The findings provide insights for optimizing manufacturing conditions for melting CPs using established sintering techniques.