Flexible Alkali-Halogen Bonding in Two Dimensional Alkali-Metal Organic Frameworks

Area of Science:

• Materials Science
• Chemistry
• Nanotechnology

Background:

• Two-dimensional metal-organic frameworks (2D MOFs) are of significant interest for advanced applications.
• Synthesizing 2D MOFs with high flexibility remains a challenge due to directional bonding in conventional coordination nodes.

Purpose of the Study:

• To develop a novel method for fabricating highly flexible 2D MOFs.
• To explore the use of isotropic alkali ions as flexible coordination points in MOF construction.

Main Methods:

• Utilized single alkali ions (specifically sodium) and dihalogenated organic molecules (2,3,6,7,10,11-hexabromotriphenylene) for on-surface synthesis.
• Employed scanning tunneling microscopy on a Au(111) surface to fabricate and characterize the resulting metal-organic frameworks.

Main Results:

• Successfully constructed sodium-based 2D MOFs on a Au(111) surface.
• Demonstrated that alkali-halogen bonding allows for tunable coordination nodes with a large deflection angle range of ±36°.
• Achieved construction of multiple 2D MOF architectures due to the flexibility of the alkali ion joints.

Conclusions:

• Single alkali ions can serve as versatile pivot joints for creating tunable 2D MOFs with unprecedented flexibility.
• The flexible alkali-halogen bonding strategy offers a new pathway for designing and constructing diverse MOF architectures.
• This work expands the toolbox for MOF engineering, enabling the development of materials with tailored properties.