Substituted 1,3,5-Triazine Hexacarboxylates as Potential Linkers for MOFs

Area of Science:

• Materials Chemistry
• Organic Synthesis
• Supramolecular Chemistry

Background:

• Metal-organic frameworks (MOFs) are advanced porous materials with applications in gas storage, separation, and catalysis.
• Hexacarboxylate linkers are essential for constructing MOFs with high surface areas and pore volumes, such as NU-109 and NU-110.
• Developing novel, elongated hexacarboxylate linkers is key to expanding the capabilities of MOF materials.

Purpose of the Study:

• To synthesize new, elongated hexacarboxylate linkers for MOF construction.
• To explore the utility of palladium-catalyzed cross-coupling reactions for linker synthesis.
• To introduce functional groups onto the linker arms for tailored MOF properties.

Main Methods:

• Synthesis of 2,4,6-tris(bromoaryl)-1,3,5-triazines as precursors.
• Palladium-catalyzed Suzuki-Miyaura and Sonogashira-Hagihara cross-coupling reactions.
• Purification and characterization of the resulting hexacarboxylate linkers.

Main Results:

• Eight new 2,4,6-tris(biphenyl) and 2,4,6-tris(phenylethynylphenyl) 1,3,5-triazines were successfully synthesized.
• Yields ranged from 40 mg to 1.1 g, demonstrating scalability.
• Five linkers incorporated additional functional groups (NO2 or OMe) on one arm.

Conclusions:

• The study successfully prepared novel hexacarboxylate linkers with extended structures.
• Palladium-catalyzed cross-coupling reactions are effective for synthesizing these complex linkers.
• The synthesized linkers are suitable for creating advanced MOFs with potentially tunable properties.