How Reproducible is the Synthesis of Zr-Porphyrin Metal-Organic Frameworks? An Interlaboratory Study

Area of Science:

• Materials Science
• Chemistry
• Crystallography

Background:

• Metal-organic frameworks (MOFs) are advanced porous materials with diverse applications.
• MOF synthesis often yields multiple crystal structures from the same precursors, complicating phase selectivity.
• Sensitivity to synthesis conditions leads to reproducibility issues, impeding MOF research and commercialization.

Purpose of the Study:

• To conduct the first interlaboratory study on the synthetic reproducibility of two zirconium-porphyrin MOFs: PCN-222 and PCN-224.
• To assess the scope of reproducibility challenges in MOF synthesis.
• To investigate variability in thermal behavior, defect content, and surface area.

Main Methods:

• Interlaboratory synthesis of PCN-222 and PCN-224 MOFs.
• Phase purity and symmetry analysis of synthesized samples.
• Characterization of thermal behavior, defect content, and surface area.

Main Results:

• Only one out of ten PCN-222 samples achieved phase purity and correct symmetry.
• Three out of ten PCN-224 samples were phase pure but lacked characteristic spatial linker order, resembling disordered dPCN-224.
• Significant variability observed in thermal properties, defect levels, and surface areas across synthesized MOF batches.

Conclusions:

• MOF synthesis reproducibility is a critical issue, particularly for complex structures like PCN-222 and PCN-224.
• The multi-variable synthesis space and flat energy landscapes of MOFs contribute to significant crystallization challenges.
• Findings underscore the need for improved synthetic control and standardization in MOF research and development.