Transitioning Formamide Solvothermal Syntheses of MOFs to Less Toxic Solvents.

Area of Science:

• Materials Science
• Green Chemistry
• Nanotechnology

Background:

• Metal-organic frameworks (MOFs) are crucial porous materials with diverse applications.
• Traditional MOF synthesis heavily relies on toxic formamide solvents, posing environmental and health concerns.
• Zinc carboxylate MOFs are particularly challenging to synthesize without formamide due to its multifaceted role.

Purpose of the Study:

• To investigate synthetic factors for formamide solvent removal in MOF synthesis.
• To develop a sustainable, formamide-free synthetic route for various MOF classes.
• To identify critical parameters for successful MOF formation without formamide.

Main Methods:

• Systematic investigation of synthetic conditions for formamide-free MOF production.
• Utilizing a tetrahydrofuran (THF)/base additive system to mimic formamide solvent functions.
• Characterization of synthesized MOFs (IRMOF-5, IRMOF-3, HKUST-1, Zn-MOF-74) for successful formamide removal.

Main Results:

• Complete formamide removal was achieved for IRMOF-5, IRMOF-3, HKUST-1, and Zn-MOF-74.
• A THF/base system effectively replicated the essential functions of formamide in MOF synthesis.
• Key determinants for formamide-free MOF formation identified: linker/metal salt solubility and base pKa.

Conclusions:

• Sustainable, formamide-free synthesis of MOFs is achievable across multiple classes.
• Understanding linker solubility, metal salt solubility, and base pKa is critical for designing new MOF syntheses.
• This work provides a foundation for developing greener MOF synthesis methodologies.